Publications

2013
Climbing up the vibrational ladder of HC15N: High-temperature near-infrared emission measurements. Journal of Molecular Spectroscopy. 2013;293-294:27-32. pub68.pdf
Ibrahim A, Predoi-Cross A, Povey C. Handling techniques for channel spectra in synchrotron-based Fourier transform spectra1. Canadian Journal of Physics. 2013;91:910-923.Abstract
Recently, the high radiance of synchrotron sources has been used to enhance FTIR spectrometer performance.However, excessive channel spectra when synchrotron sources are used degrade the quality of retrieved spectral parameters.We have investigated seven different techniques for handling channel spectra. These techniques were used to reducechannel spectra for a test group of seven samples of CO2 mixed with air recorded using the synchrotron source at theCanadian Light Source. The increases in signal to noise ratio (SNR) of spectra handled with each technique were calculated.SNR results showed that transmission spectra, produced using synthetic background spectra with simulated channelspectra, achieved the highest SNR improvement. However, when the spectra groups were fitted using a nonlinear leastsquare fit algorithm, the technique using channel spectra fitting produced the smallest fitting residual. Moreover, theretrieved intensities and air broadening coefficients of 21 spectral lines showed that the spectral fitting technique producedthe most accurate values as compared to the HITRAN 2008 database (Rothman et al. J. Quant. Spectrosc. Radiat. Transfer, 110,533 (2009)). Although the spectral fitting technique was accurate in retrieving spectral line parameters, applying thetechnique at wider spectral ranges reduced this accuracy.
pub65.pdf
Hashemi R, Rozario H, Ibrahim A, Predoi-Cross A. Line shape study of the carbon dioxide laser band I1. Canadian Journal of Physics. 2013;91.Abstract
The spectral line parameters of carbon dioxide have been measured in the laser band I (00011 ¢ 10001) centred at 10.4 m. The spectra were recorded at room temperature using the spectroscopic instrumentation at the far-infrared beamline, Canadian Light Source, Saskatoon, Sask. The spectral line intensities, air- and self- broadened Lorentz half widths, and pressureinduced shift coefficients were retrieved for 48 spectral lines using a multispectrum fit technique (Benner et al. J. Quant. Spectrosc. Radiat. Transfer, 53, 705 (1995)). Line parameters were retrieved using the Voigt and speed-dependent Voigt models. The deviations between our results and other results reported in the literature and in the HITRAN08 (Rothman et al. J. Quant. Spectrosc. Radiat. Transfer, 110, 533 (2009)) database were examined and discussed. The effect of errors in fitting channel spectra parameters was examined and found to be mitigated by the inclusion of channels in the multispectral fit.
pub66.pdf
Povey C, Guillorel-Obregon M, Predoi-Cross A, Ivanov SV, Buzykin OG, Thibault F. Low pressure line shape study of nitrogen-perturbed acetylene transitions in the ν1+ ν3band over a range of temperatures1. Canadian Journal of Physics. 2013;91:896-905.Abstract
Six nitrogen-perturbed transitions of acetylene within the 1 + 3 absorption band have been recorded using athree-channel diode laser spectrometer. The goal being an improved understanding of both broadening and narrowing effectsof low-pressure acetylene under the influence of nitrogen gas. To this end we have examined C2H2 spectra using a hard collisionRautian profile over a range of five temperatures (213–333 K) and five pressures (5–40 Torr). From these fits we have obtained theN2-broadening and narrowing coefficients of C2H2 and examined their temperature dependence. The experimentally measurednarrowing coefficients have been used to estimate the nitrogen diffusion coefficients (D12) and are presented within. Thebroadening coefficients and corresponding temperature dependence exponents have also been compared to that of calculationscompleted using a classical impact approach on an ab initio potential energy surface. We have observed good agreementbetween our theoretical and experimental results.
pub67_0.pdf
Smith MAH, Benner CD, Predoi-Cross A, Malathy Devi V. Air- and self-broadened half widths, pressure-induced shifts, and line mixing in the ν2 band of 12CH4. Journal of Quantitative Spectroscopy and Radiative Transfer. 2013;133:217-234.Abstract
Lorentz self- and air-broadened half width and pressure-induced shift coefficients andtheir dependences on temperature have been measured from laboratory absorptionspectra for nearly 130 transitions in the ν2 band of 12CH4. In addition line mixingcoefficients (using the relaxation matrix element formalism) for both self- and air-broadening were experimentally determined for the first time for a small number oftransitions in this band. Accurate line positions and absolute line intensities were alsodetermined. These parameters were obtained by analyzing high-resolution (0.003 to0.01 cm1) laboratory spectra of high-purity natural CH4 and air-broadened CH4 recordedat temperatures between 226 and 297 K using the McMath–Pierce Fourier transformspectrometer (FTS) located at the National Solar Observatory on Kitt Peak, Arizona.A multispectrum nonlinear least squares technique was used to fit short (5–15 cm1)spectral intervals in 24–29 spectra simultaneously. Parameters were determined for ν2transitions up to J″¼16. The variations of the measured broadening and shift parameterswith the rotational quantum number index and tetrahedral symmetry species areexamined. The present results are also compared with previous measurements availablein the literature.Published by Elsevier Ltd.
pub64.pdf
2012
Rozario H, Garber J, Povey C, Hurtmans D, Buldyreva J, Predoi-Cross A. Experimental and theoretical study of N2-broadened acetylene line parameters in the ν1 + ν3band over a range of temperatures. Molecular Physics. 2012;110:2645-2663.Abstract
N2-broadened line widths and N2-pressure induced line shifts have been measured for transitions in the 1þ3band of acetylene at seven temperatures in the range 213–333K to obtain the temperature dependences ofbroadening and shift coefficients. For the room-temperature spectra the line mixing effects have been alsoinvestigated. The Voigt and hard-collision line profile models were used to retrieve the line parameters. Allspectra were recorded using a 3-channel tuneable diode laser spectrometer. The line-broadening and line-shiftingcoefficients as well as their temperature-dependence parameters have been also evaluated theoretically, in theframe of a semi-classical approach based on an exponential representation of the scattering operator, anintermolecular potential composed of electrostatic quadrupole–quadrupole and pairwise atom–atom interactionsas well as on exact trajectories driven by an effective isotropic potential.
pub61.pdf
Predoi-Cross A, Herman M, Fusina L, Di Lonardo G. The infrared spectrum of13C2H2in the 60–2600 cm−1region: bending states up tov4 + v5 = 4. Molecular Physics. 2012;110:2621-2632.Abstract
The vibration–rotation spectra of 13C substituted acetylene, 13C2H2, have been recorded in the region between 60and 2600cm1 at an effective resolution ranging from 0.001 to 0.006cm1. Three different instruments were usedto collect the experimental data in the extended spectral interval investigated. In total 9529 rotation vibrationtransitions have been assigned to 101 bands involving the bending states up to vtot¼v4þv5¼4, allowing thecharacterization of the ground state and of 33 vibrationally excited states. All the bands involving states up tovtot¼3 have been analyzed simultaneously by adopting a model Hamiltonian which takes into account thevibration and rotation l-type resonances. The derived spectroscopic parameters reproduce the transitionwavenumbers with a RMS value of the order of the experimental uncertainty. Using the same model, largerdiscrepancies between observed and calculated values have been obtained for transitions involving states withvtot¼4. These could be satisfactorily reproduced only by adopting a set of effective constants for each vibrationalmanifold, in addition to the previously determined parameters, which were constrained in the analysis.
pub63.pdf
Povey C, Predoi-Cross A, Hurtmans DR. Low-pressure line shape study of acetylene transitions in theν1 + ν2 + ν4 + ν5band over a range of temperatures. Molecular Physics. 2012;110:2633-2644.Abstract
In this study we have retrieved the self-broadened widths, self-pressure-induced shifts, and Dicke narrowingcoefficients for 20 R-branch transitions in the 1þ2þ4þ5 band of acetylene. The spectra were recorded usinga three-channel diode laser spectrometer, a temperature-controlled cell of fixed length and a second, roomtemperature cell. The soft collision (Galatry) and hard collision (Rautian) profiles with inclusion of line mixingeffects were used to retrieve the line parameters. We determined the temperature dependencies for linebroadening, shift, and Dicke narrowing coefficients. We performed comparisons between our retrieved lineparameters and published line parameters for acetylene transitions.
pub62.pdf
Predoi−Cross A, Herman M, Fusina L, Di Lonardo G. The far infrared spectrum of trans-formic acid: An extension up to 175cm−1. Journal of Quantitative Spectroscopy and Radiative Transfer. 2012;113:1134-1137.Abstract
The far infrared spectrum of HCOOH was recorded at a high resolution (0.0009 cm1)and long path length (72 m) at the far-infrared beamline, Canadian Light Source. Spectrawere recorded in the region 62–300 cm1, showing transitions from the trans-isomer.Ground state rotational transitions with Ka up to 30, were identified up to 175 cm1,extending the observation reported in the literature. A total of 3321 transitions wereassigned and fitted together with previous (4149) published data. An improved set ofrotational parameters was obtained adopting the symmetric top (A) reduction of therotational Hamiltonian in the Ir representation. The newly measured far infraredtransitions allowed the determination of all diagonal and off diagonal 8th orderparameters L and of some of the diagonal 10th order parameters P.& 2012 Elsevier Ltd. All rights reserved.
pub60.pdf
2011
Astrophysics and Atmospheric Sciences at the CLS: The Far Infrared Beamline. Physics in Canada. 2011;67:11-16. pub55.pdf
Women in physics. In: The Encyclopedia of Women in Today's World. SAGE Publications ; 2011. women_in_physics.pdf
Jacquinet-Husson N, Crepeau L, Armante R, Boutammine C, Chédin A, Scott NA, Crevoisier C, Capelle V, Boone C, Poulet-Crovisier N, et al. The 2009 edition of the GEISA spectroscopic database. Journal of Quantitative Spectroscopy and Radiative Transfer. 2011;112:2395-2445.Abstract
The updated 2009 edition of the spectroscopic database GEISA (Gestion et Etude desInformations Spectroscopiques Atmosphe´ riques; Management and Study of AtmosphericSpectroscopic Information) is described in this paper. GEISA is a computer-accessiblesystem comprising three independent sub-databases devoted, respectively, to: lineparameters, infrared and ultraviolet/visible absorption cross-sections, microphysicaland optical properties of atmospheric aerosols. In this edition, 50 molecules are involvedin the line parameters sub-database, including 111 isotopologues, for a total of 3,807,997entries, in the spectral range from 106 to 35,877.031 cm1.The successful performances of the newgeneration of hyperspectral sounders dependultimately on the accuracy to which the spectroscopic parameters of the optically activeatmospheric gases are known, since they constitute an essential input to the forwardradiative transfer models that are used to interpret their observations. Currently, GEISA isinvolved in activities related to the assessment of the capabilities of IASI (InfraredAtmospheric Sounding Interferometer; <a href="http://smsc.cnes.fr/IASI/index.htm" rel="nofollow">http://smsc.cnes.fr/IASI/index.htm</a>) on board theMETOP European satellite through the GEISA/IASI database derived from GEISA. Since theMetop-A (<a href="http://www.eumetsat.int" rel="nofollow">http://www.eumetsat.int</a>) launch (19 October 2006), GEISA is the referencespectroscopic database for the validation of the level-1 IASI data. Also, GEISA is involvedin planetary research, i.e., modeling of Titan’s atmosphere, in the comparison withobservations performed by Voyager, or by ground-based telescopes, and by the instru-ments on board the Cassini–Huygens mission.GEISA, continuously developed and maintained at LMD (Laboratoire de Me´te´orologieDynamique, France) since 1976, is implemented on the IPSL/CNRS (France) ‘‘Ether’’Products and Services Centre WEB site (<a href="http://ether.ipsl.jussieu.fr" rel="nofollow">http://ether.ipsl.jussieu.fr</a>), where all archivedspectroscopic data can be handled through general and user friendly associated manage-ment software facilities.More than 350 researchers are registered for on line use of GEISA.&amp; 2011 Elsevier Ltd. All rights reserved.
geisa.pdf
Predoi-Cross A, Herman M, Fusina L, Lonardo DG. The far-infrared spectrum of 12C2HD. Molecular Physics. 2011;109:559-563.Abstract
The infrared spectrum of 12C2HD has been studied using synchrotron radiation at the far-infrared beam line,Canadian Light Source, Saskatoon, Canada. The spectra were recorded at a resolution of 0.00096 cm 1 in the 60to 360 cm 1 range using a Bruker IFS 125 Fourier transform spectrometer. In total, 821 vibration rotation lineswere observed and assigned to the P(J), Q(J) and R(J) transitions of the 5 4 difference band and associatedhot bands with J00 up to 35 and ( 4þ 5) up to 3. These new transitions were analysed together with 4518transitions involving bending states with ( 4þ 5) up to 3 available in the literature. The spectroscopic parametersobtained from the fit reproduce 4909 transitions with a standard deviation of 0.00028 cm 1. The 5 4 bands of13CH12CD and 12CH13CD were also detected and analysed.
pub51.pdf
Moruzzi G, Murphy RJ, Vos J, Lees RM, Predoi-Cross A, Billinghurst BE. Fourier transform synchrotron spectroscopy of torsional and CO-stretching bands of CH317OH. Journal of Molecular Spectroscopy. 2011;268:211-220.Abstract
The Fourier transform spectrum of the CH317OH isotopologue of methanol has been recorded in the65–1200 cm1 spectral region at a resolution of 0.00096 cm1 using synchrotron source radiation atthe Canadian Light Source. Here we present an extension to higher torsional states of our investigationof the torsion–rotation transitions within the small-amplitude vibrational ground state, now includingassignments of more than 16 500 lines involving quantum numbers in the ranges vt 6 3, J 6 30 and|K| 6 12, as well as a study of the strong CO-stretching band centered at 1020 cm1. Energy term valueshave been determined for assigned ground and CO-stretching levels by use of the Ritz program, and havebeen fitted to series expansions in powers of J(J + 1) to determine substate origins and effective B values.Several Fermi anharmonic and Coriolis level-crossing resonances coupling the CO stretch with high tor-sional ground-state levels have been identified and characterized. The study is motivated by astrophys-ical applications, with a principal aim being the compilation of an extensive set of energy term values topermit prediction of astronomically observable sub-millimetre transitions to within an uncertainty of afew MHz.
pub56.pdf
Povey C, Predoi-Cross A, Hurtmans DR. Line shape study of acetylene transitions in the ν1+ν2+ν4+ν5 band over a range of temperatures. Journal of Molecular Spectroscopy. 2011;268:177-188.Abstract
In this study we have retrieved the line intensities, self broadened widths, pressure-induced shifts andselected line mixing coefficients for 20 R-branch transitions in the m1 + m2 + m4 + m5 band of acetylene.The spectra were recorded using our 3-channels diode laser spectrometer, a temperature controlled cellof fixed length and a second, room temperature cell. The Voigt and speed-dependent Voigt profiles withinclusion of line mixing effects were used to retrieve the line parameters. We determined the tempera-ture dependencies for line broadening, shift and line mixing coefficients.
pub58.pdf
Smith MAH, Benner CD, Predoi-Cross A, Malathy Devi V. A multispectrum analysis of the ν4 band of 13CH4: Widths, shifts, and line mixing coefficients. Journal of Quantitative Spectroscopy and Radiative Transfer. 2011;112:952-968.Abstract
Line positions, Lorentz air-broadened half width and air pressure-induced shift coeffi-cients have beenmeasured for nearly 200 transitions in the n4 band of 13CH4 from high-resolution spectra recorded with the McMath-Pierce Fourier transform spectrometer.Threeroom temperature spectra of 13CH4 used in the previous study of Malathy Devi et al.(Air-broadened Lorentz halfwidths and pressure-induced line shifts in the n4 band of13CH4. Appl. Opt. 1988; 27: 2296–2308) were analyzed together with a large number ofadditional spectra of self- and air-broadened CH4 recorded at 210–314 K and one room-temperature spectrum of self-broadened 13CH4. Analyses applying the multispectrumnonlinear least squares fitting technique were performed to retrieve the spectral lineparameters. In addition to air-broadened half width and shift coefficients, self-broadenedhalf width and shift coefficients were determined for at least 56 13CH4n4 transitions. Off-diagonal relaxation matrix element coefficients for air-broadened line mixing were alsodetermined for 28 pairs of P and R transitions in a number of J manifolds, and mixingparameters for self-broadening were also determined for some of these pairs. Tempera-ture-dependences of the pressure-induced shift and mixing parameters for the 13CH4lines could not be determined from the spectra used in the present analysis, buttemperature dependences of the half width coefficients were determined for thestrongest transitions. The results of this study are compared with other studies of air-and self-broadened 13CH4 and 12CH4.
paper52.pdf
Ceausu-Velcescu A, Pracna P, Predoi-Cross A. Rovibrational spectra of DCF3 in the 1000cm−1 region: The ν5=1 and ν6=2 levels revisited. Journal of Molecular Spectroscopy. 2011;267:150-157.Abstract
The degenerate fundamental vibrational level v5 = 1 (975.51 cm 1, E symmetry) and the overtone vibrationallevel v6 = 2 (1004.06/1005.98 cm 1, A1 + E symmetry) were reinvestigated with inclusion of theirinter-vibrational couplings: the anharmonic Fermi interaction (DK ¼ 0, RtDlt ¼ Dl5 þ Dl6 ¼ 3), the second-order Coriolis resonance (DK ¼ 1, RtDlt ¼ 1), and the second-order a-resonance (DK ¼ 2,RtDlt ¼ 1). This required significant extension of assignments to high J and K rotational states whereresonant crossings due to the latter two interactions occur. The newly assigned data from Fourier-transformIR spectroscopy were combined with rotational and laser-sideband rovibrational data pertaining tothe v5 = 1 vibrational level, which were used already in a previous analysis, in a fully quantitative simultaneousfit.
pub57.pdf
Bouanich JP, Predoi-Cross A. Theoretical calculations for line-broadening and pressure-shifting in theν1 + ν2 + ν4 + ν5band of acetylene over a range of temperatures. Molecular Physics. 2011;109:2071-2081.Abstract
Semiclassical calculations of self-broadening and self-induced pressure shift coefficients in the 1þ 2þ 4þ 5 band of C2H2 have been performed by considering, in addition to the main electrostatic quadrupole–quadrupole interaction, a simple anisotropic dispersion contribution, leading to results in overall satisfactory agreement with recent measurements [C. Povey, A. Predoi-Cross and D.R. Hurtmans, J. Mol. Spectrosc., 268, 177 (2011)]. In these calculations we have used the mean relative velocity and also considered the Maxwell–Boltzmann distribution of relative velocities. From the theoretical results obtained at different temperatures ranging from 200 to 350 K, we have determined temperature exponents of the broadenings using a simple power law, as well ascoefficients of empirical linear and quadratic temperature dependences for the line shifts. These theoretical exponents and linear coefficients, derived from averaging over the distribution of velocities and from the mean thermal velocity, are significantly different and they are compared with those obtained from measurements of broadening coefficients and line shifts performed in a comparable temperature range [C. Povey, A. Predoi-Cross and D.R. Hurtmans, J. Mol. Spectrosc., 268, 177 (2011)]. The theoretical variation of the self-shifts with temperature is not linear and can be well fitted by a quadratic polynomial.
pub59.pdf
2010
Amyay B, Herman M, Fayt A, Fusina L, Predoi-Cross A. High resolution FTIR investigation of 12C2H2 in the FIR spectral range using synchrotron radiation. Chemical Physics Letters. 2010;491:17-19.Abstract
FIR spectra of C2H2 have been recorded at 0.00096 cm1 spectral resolution using the Canadian LightSource synchrotron facility. The analysis allowed us to assign 731 new vibration–rotation lines from48 bands in 12C2H2, 38 of which are reported for the first time. Two additional bands are assigned to13CH12CH. The measured line positions and calculated spectra can be made available to help in theremote sensing of acetylene in the terahertz spectral range.
pub49.pdf
Smith MAH, Chris Benner D, Predoi-Cross A, Malathy Devi V. Multispectrum analysis of 12CH4 in the ν4 spectral region: II. Self-broadened half widths, pressure-induced shifts, temperature dependences and line mixing. Journal of Quantitative Spectroscopy and Radiative Transfer. 2010;111:1152-1166.Abstract
Accurate values for line positions, absolute line intensities, self-broadened half widthand self-pressure-induced shift coefficients have been measured for over 400 allowedand forbidden transitions in the n4 band ofmethane (12CH4). Temperature dependencesof half width and pressure-induced shift coefficients were also determined for many ofthese transitions. The spectra used in this study were recorded at temperatures between210 and 314K using the National Solar Observatory’s 1m Fourier transform spectro-meter at the McMath-Pierce solar telescope. The complete data set included 60 high-resolution (0.006–0.01cm1) absorption spectra of pure methane and methane mixedwith dry air. The analysis was performed using amultispectrum nonlinear least squarescurve fitting technique where a number of spectra (20 or more) were fit simultaneouslyin spectral intervals 5–15cm1 wide. In addition to the line broadening and shiftparameters, line mixing coefficients (using the off-diagonal relaxation matrix elementformalism) were determined for more than 50 A-, E-, and F-species transition pairs in Jmanifolds of the P- and R-branches. The measured self-broadened half width and self-shift coefficients, their temperature dependences and the line mixing parameters arecompared to self-broadening results available in the literature and to air-broadenedparameters determined for these transitions from the same set of spectra.
pub46.pdf
Pracna P, Ceausu-Velcescu A, Predoi-Cross A, Urban Štěpán. Rovibrational spectroscopy of the Fermi-interacting ν4=1 and ν3=ν6=1 levels of DCF3. Journal of Molecular Spectroscopy. 2010;259:1-10.Abstract
The high-resolution infrared spectrum of deuterated fluoroform (DCF3) was studied in the 700 and1200 cm1 regions, with the aim of assigning and analyzing the m4 CF3 asymmetric stretching vibration.The Fermi-type anharmonic coupling between the m4 = 1 and m3 = m6 = 1 rovibrational levels, already men-tioned in an early work of Ruoff et al. [Spectrochimica Acta Part A 31A (1975) 1099–1100], was studiedhere for the first time under high resolution. Assignments in the m3 + m6/m4 band system were confirmedand extended by the identification of the m3 + m6  m6 and m4–m6 bands in the 700 cm1 region, the latterbeing enhanced near the Fermi crossings of the studied levels. Data from both the hot and differencebands were included in the analysis. The close separation of the studied vibrational levels of about14.8 cm1 produces a large variety of resonance crossings which involve levels with Dk ¼ 0; ... ; 6.Besides the Fermi (Dk ¼ 0; Dl ¼ 0) and Coriolis (Dk ¼1; Dl ¼2) resonances, they were accountedfor by inclusion of additional higher-order (Dk ¼2; Dl ¼2 and Dk ¼3; Dl ¼ 0) interaction termsbetween the vibrational states. The least-squares fit of more that 16,000 vibration-rotation transitionsprovides a quantitative reproduction of data in all bands.
pub45.pdf
Predoi-Cross A, Ibrahim A, Herman M, Fusina L, Nivellini G, Di Lonardo G. The high resolution infrared spectrum of the v4 band of 1,1,1-trifluoroethane. Molecular Physics. 2010;108:2303-2307.Abstract
The v4 band of 1,1,1-trifluoroethane (CH3CF3) has been studied using synchrotron radiation at the far-infraredbeamline, Canadian Light Source. The spectra were recorded at a resolution of 0.00096cm1 in the spectralrange 800 to 860cm1 using a Bruker IFS125 FT spectrometer. Altogether 2785 lines were assigned to qPK(J )and qRK(J ) transitions with J 00 up to 71 and K up to 45. The qQK(J ) sub-branches are too congested andoverlapped to other hot-band Q branches to be analysed. A Watson-type Hamiltonian containing the usual termsup to the 6th power in the angular momentum operators was used in the analysis. The spectroscopic parametersobtained from the fit reproduce 2636 transitions with a standard deviation of about 0.00016cm1.
pub48.pdf
Moruzzi G, Murphy RJ, Lees RM, Predoi-Cross A, Billinghurst BE. High-resolution synchrotron-based Fourier transform spectroscopy of CH317OH in the 120-350 cm-1 far-infrared region. Molecular Physics. 2010;108:2343-2353.Abstract
The Fourier transform spectrum of the CH317OH isotopologue of methanol has been recorded in the 120–350 cm 1 far-infrared region at a resolution of 0.00096 cm 1 using synchrotron source radiation at the CanadianLight Source. The study, motivated by astrophysical applications, is aimed at generating a sufficiently accurateset of energy level term values for the ground vibrational state to allow prediction of the centres of thequadrupole hyperfine multiplets for astronomically observable sub-millimetre transitions to within anuncertainty of a few MHz. To expedite transition identification, a new function was added to the Ritz programin which predicted spectral line positions were generated by an adjustable interpolation between the knownassignments for the CH316OH and CH318OH isotopologues. By displaying the predictions along with theexperimental spectrum on the computer monitor and adjusting the predictions to match observed features, rapidassignment of numerous CH317OH sub-bands was possible. The least squares function of the Ritz program wasthen used to generate term values for the identified levels. For each torsion-K-rotation substate, the term valueswere fitted to a Taylor-series expansion in powers of J(Jþ1) to determine the substate origin energy and effectiveB-value. In this first phase of the study we did not attempt a full global fit to the assigned transitions, but insteadfitted the sub-band J-independent origins to a restricted Hamiltonian containing the principal torsional andK-dependent terms. These included structural and torsional potential parameters plus quartic distortional andtorsion–rotation interaction terms.
pub47.pdf
Predoi-Cross A, Liu W, Murphy R, Povey C, Gamache RR, Laraia AL, McKellar ARW, Hurtmans DR, Malathy Devi V. Measurement and computations for temperature dependences of self-broadened carbon dioxide transitions in the 30012←00001 and 30013←00001 bands. Journal of Quantitative Spectroscopy and Radiative Transfer. 2010;111:1065-1079.Abstract
Using a Fourier transform spectrometer setup we have measured the self-broadenedhalf width, pressure shift, and line asymmetry coefficients for transitions in the30012’00001 and 30013’00001 vibrational bands of carbon dioxide for four differenttemperatures. A total of 46 pure CO2 spectra were recorded at 0.008 and 0.009cm1resolution and at pressures varying from a few Torr to nearly an atmosphere. Theindividual spectral line profiles have been fitted by a Voigt profile and a speed-dependent Voigt profile, to which we have added dispersion profiles to account forweak line mixing. A comparison of the sets of results obtained for each band showed novibrational dependence of the broadening coefficients. The self-broadening and self-shift coefficients are compared to semiclassical calculations based on the Robert–Bonamy formalism and were found to be in good agreement. The line asymmetryresults are compared to linemixing calculations based on the Energy Corrected Sudden(ECS) and Exponential Power Gap models.
pub50.pdf
2009
Povey C, Predoi-Cross A. Computations of temperature dependences for line shape parameters in the 30012←00001 and 30013←00001 bands of pure CO2. Journal of Molecular Spectroscopy. 2009;257:187-199.Abstract
In this study, we have calculated the broadening and first order line mixing parameters for over 100transitions in the 30012 00001 and 30013 00001 bands of carbon dioxide. The calculations wereperformed over the 193–323 K temperature range for pure CO2 and lean mixtures of CO2 and air. Theelements of the relaxation matrices were calculated at the appropriate physical conditions using theExponential Power Gap (EPG) and Energy Corrected Sudden (ECS) scaling laws. We have compared ourcalculated low pressure line mixing parameters and the broadening coefficients with experimentalresults from two previous studies in our group available at 217, 234, 258 and 296 K. At all temperatures,the calculated broadening coefficients were also compared with those available in the HITRAN database. 2009 Elsevier Inc. All rights reserved
Rothman LS, Gordon IE, Barbe A, Benner CD, Bernath PF, Birk M, Boudon V, Brown LR, Campargue A, Champion JP, et al. The HITRAN 2008 molecular spectroscopic database. Journal of Quantitative Spectroscopy and Radiative Transfer. 2009;110:533-572.Abstract
This paper describes the status of the 2008 edition of the HITRAN molecularspectroscopic database. The new edition is the first official public release since the2004 edition, although a number of crucial updates had been made available onlinesince 2004. The HITRAN compilation consists of several components that serve as inputfor radiative-transfer calculation codes: individual line parameters for the microwavethrough visible spectra of molecules in the gas phase; absorption cross-sections formolecules having dense spectral features, i.e. spectra in which the individual lines arenot resolved; individual line parameters and absorption cross-sections for bands in theultraviolet; refractive indices of aerosols, tables and files of general properties associatedwith the database; and database management software. The line-by-line portion of the database contains spectroscopic parameters for 42 molecules including many of their isotopologues.
Predoi-Cross A, McKellar ARW, Benner CD, Devi MV, Gamache RR, Miller CE, Toth RA, Brown LR. Temperature dependences for air-broadened Lorentz half-width and pressure shift coefficients in the 30013←00001 and 30012←00001 bands of CO2near 1600 nm This article is part of a Special Issue on Spectroscopy at the University of New Brunswick in hono. Canadian Journal of Physics. 2009;87:517-535.Abstract
In this study, 39 high-resolution spectra of pure and air-broadened CO2 recorded at temperatures between 215 and294 K were analyzed using a multispectrum nonlinear least-squares technique to determine temperature dependences of air-broadened Lorentz half-width and air-induced pressure shift coefficients for over 100 individual 12C16O2 transitions in the30012/00001 (at 6348 cm–1) and 30013/00001 (at 6228 cm–1) bands. Data were recorded with two different Fourier trans-form spectrometers (Kitt Peak FTS at the National Solar Observatory in Arizona and the Bomem FTS at NRC, Ottawa), withabsorption path lengths ranging between 25 and 121 m. The sample pressures varied between 11 torr (pure CO2) and 924 torr(CO2-air) with volume mixing ratios of CO2 in air between*1.5% and 11% (1 torr = 133.322 4 Pa). To minimize systematicerrors and increase the accuracy of the retrieved parameters, a constrained multispectrum nonlinear least-squares fitting tech-nique was used to include theoretical quantum mechanical expressions for the rovibrational energies and intensity parametersrather than retrieving the individual positions and intensities line by line. The results suggest no detectable vibrational de-pendence for the temperature dependences for the air-broadened Lorentz half-width coefficients and the air-induced pressureshift coefficients. The half-width coefficients and temperature dependence exponents were modeled using semiclassical cal-culations based upon the Robert–Bonamy formalism. A good agreement is seen between the measurements and theoreticalcalculations. Beyond |m| = 26, a simple scaling factor (0.96) has been applied to the calculated half-width coefficients tomatch the experimental measurements.
Predoi-Cross A, Rohart F, Bouanich J-P, Hurtmans DR. Xenon-broadened CO line shapes in the fundamental band at 349 KThis article is part of a Special Issue on Spectroscopy at the University of New Brunswick in honour of Colan Linton and Ron Lees. Canadian Journal of Physics. 2009;87:485-498.Abstract
We present a line shape analysis of the P(2) and P(7) transitions of CO broadened by Xe in the fundamentalband. The spectra were recorded at 349 K using a difference frequency laser spectrometer. To obtain information on theinfluence of Dicke narrowing, relaxation speed dependence, and line mixing effects, several models for implementation ofDicke narrowing and (or) speed-dependent effects are discussed. From experimental data analysis, we conclude that lineshape models taking into account the Dicke effect only fail in the high pressure regime and lead to optical diffusion pa-rameters that are much larger than the kinetic diffusion ones. On the contrary, a fair interpretation of data is obtained fromspeed-dependent models, so that it is possible to derive a quantitative estimate of optical diffusion effects that appearmuch smaller than the kinetic diffusion ones. Xe-broadening coefficients of CO lines in the fundamental band at 297 and349 K are calculated from a semiclassical formalism involving successively two intermolecular potentials, the atom-atomLennard-Jones model, and a three-term expansion of Legendre polynomials with four adjustable parameters.
Lees RM, Murphy R-J, Moruzzi G, Predoi-Cross A, Xu L-H, Appadoo DRT, Billinghurst B, Goulding RRJ, Zhao S. Fourier transform spectroscopy of the CO-stretching band of O-18 methanol. Journal of Molecular Spectroscopy. 2009;256:91-98.Abstract
The high-resolution Fourier transform spectrum of the m8 CO-stretching band of CH318OH between 900and 1100 cm1 has been recorded at the Canadian Light Source (CLS) synchrotron facility in Saskatoon,and the majority of the torsion–rotation structure has been analyzed. For the mt = 0 torsional ground state,subbands have been identified for K values from 0 to 11 for A and E torsional symmetries up to J valuestypically well over 30. For mt =1, A and E subbands have been assigned up to K = 7, and several mt = 2 sub-bands have also been identified. Upper-state term values determined from the assigned transitions usingthe Ritz program have been fitted to J(J + 1) power-series expansions to obtain substate origins and sets ofstate-specific parameters giving a compact representation of the substate J-dependence. The mt = 0 sub-band origins have been fitted to effective molecular constants for the excited CO-stretching state and atorsional barrier of 377.49(32) cm1 is found, representing a 0.89% increase over the ground-state value.The vibrational energy for the CO-stretch state was found to be 1007.49(7) cm1. A number of subband-wide and J-localized perturbations have been seen in the spectrum, arising both from anharmonic andCoriolis interactions, and several of the interacting states have been identified. 2009 Elsevier Inc. All rights reserved.
Smith MAH, Benner CD, Predoi-Cross A, Devi MV. Multispectrum analysis of 12CH4 in the ν4 band: I. Journal of Quantitative Spectroscopy and Radiative Transfer. 2009;110:639-653.Abstract
Lorentz air-broadened half widths, pressure-induced shifts and their temperaturedependences have been measured for over 430 transitions (allowed and forbidden) inthe n4 band of 12CH4 over the temperature range 210–314K. A multispectrum non linearleast squares fitting technique was used to simultaneously fit a large number of high-resolution (0.006–0.01cm1) absorption spectra of pure methane and mixtures ofmethane diluted with dry air. Linemixing was detected for pairs of A-, E-, and F-speciestransitions in the P- and R-branch manifolds and quantified using the off-diagonalrelaxation matrix elements formalism. The measured parameters are compared toair- and N2-broadened values reported in the literature for the n4 and other bands. Thedependence of the various spectral line parameters upon the tetrahedral symmetryspecies and rotational quantum numbers of the transitions is discussed. All data used inthe present work were recorded using the McMath–Pierce Fourier transform spectro-meter located at the National Solar Observatory on Kitt Peak.Published by Elsevier Ltd.
Predoi-Cross A, McKellar ARW, Benner CD, Devi MV, Gamache RR, Miller CE, Toth RA, Brown LR. Temperature dependences for air-broadened Lorentz half-width and pressure shift coefficients in the 30013←00001 and 30012←00001 bands of CO2near 1600 nm. Canadian Journal of Physics. 2009;87:517-535.Abstract
In this study, 39 high-resolution spectra of pure and air-broadened CO2 recorded at temperatures between 215 and294 K were analyzed using a multispectrum nonlinear least-squares technique to determine temperature dependences of air-broadened Lorentz half-width and air-induced pressure shift coefficients for over 100 individual 12C16O2 transitions in the30012/00001 (at 6348 cm–1) and 30013/00001 (at 6228 cm–1) bands. Data were recorded with two different Fourier trans-form spectrometers (Kitt Peak FTS at the National Solar Observatory in Arizona and the Bomem FTS at NRC, Ottawa), withabsorption path lengths ranging between 25 and 121 m. The sample pressures varied between 11 torr (pure CO2) and 924 torr(CO2-air) with volume mixing ratios of CO2 in air between*1.5% and 11% (1 torr = 133.322 4 Pa). To minimize systematicerrors and increase the accuracy of the retrieved parameters, a constrained multispectrum nonlinear least-squares fitting tech-nique was used to include theoretical quantum mechanical expressions for the rovibrational energies and intensity parametersrather than retrieving the individual positions and intensities line by line. The results suggest no detectable vibrational de-pendence for the temperature dependences for the air-broadened Lorentz half-width coefficients and the air-induced pressureshift coefficients. The half-width coefficients and temperature dependence exponents were modeled using semiclassical cal-culations based upon the Robert–Bonamy formalism. A good agreement is seen between the measurements and theoreticalcalculations. Beyond |m| = 26, a simple scaling factor (0.96) has been applied to the calculated half-width coefficients tomatch the experimental measurements.
Predoi-Cross A, Rohart F, Bouanich J-P, Hurtmans DR. Xenon-broadened CO line shapes in the fundamental band at 349 K. Canadian Journal of Physics. 2009;87:485-498.Abstract
We present a line shape analysis of the P(2) and P(7) transitions of CO broadened by Xe in the fundamentalband. The spectra were recorded at 349 K using a difference frequency laser spectrometer. To obtain information on theinfluence of Dicke narrowing, relaxation speed dependence, and line mixing effects, several models for implementation ofDicke narrowing and (or) speed-dependent effects are discussed. From experimental data analysis, we conclude that lineshape models taking into account the Dicke effect only fail in the high pressure regime and lead to optical diffusion pa-rameters that are much larger than the kinetic diffusion ones. On the contrary, a fair interpretation of data is obtained fromspeed-dependent models, so that it is possible to derive a quantitative estimate of optical diffusion effects that appearmuch smaller than the kinetic diffusion ones. Xe-broadening coefficients of CO lines in the fundamental band at 297 and349 K are calculated from a semiclassical formalism involving successively two intermolecular potentials, the atom-atomLennard-Jones model, and a three-term expansion of Legendre polynomials with four adjustable parameters.
2008
Predoi-Cross A, Unni AV, Liu W, Schofield I, Holladay C, McKellar ARW, Hurtmans D. Corrigendum to “Line shape parameters measurement and computations for self-broadened carbon dioxide transitions in the 30012←00001 and 30013←00001 bands, line mixing and speed dependence". Journal of Molecular Spectroscopy. 2008;249:72.Abstract
n/a
Predoi-Cross A, Holladay C, Heung H, Bouanich J-P, Mellau GC, Keller R, Hurtmans DR. Nitrogen-broadened lineshapes in the oxygen A-band: Experimental results and theoretical calculations. Journal of Molecular Spectroscopy. 2008;251:159-175.Abstract
We report measurements for N2-broadening, pressure-shift and line mixing coefficients for 55 oxygen transitions in the A-bandretrieved using a multispectrum fitting technique. Nineteen laboratory absorption spectra were recorded at 0.02 cm1 resolution usinga multi-pass absorption cell with path length of 1636.9 cm and the IFS 120 Fourier transform spectrometer located at Justus-Liebig-Uni-versity in Giessen, Germany. The total sample pressures ranged from 8.8 to 3004.5 Torr with oxygen volume mixing ratios in nitrogenranging between 0.057 and 0.62. An Exponential Power Gap (EPG) scaling law was used to calculate the N2-broadening and N2-linemixing coefficients.The line broadening and shift coefficients for the A-band of oxygen self-perturbed and perturbed by N2 are modeled using semiclas-sical calculations based on the Robert–Bonamy formalism and two intermolecular potentials. These potentials involve electrostatic con-tributions including the hexadecapole moment of the molecules and (a) a simple dispersion contribution with one adjustable parameter tofit the broadening coefficients or (b) the atom–atom Lennard-Jones model without such adjustable parameters. The first potential leadsto very weak broadening coefficients for high J transitions whereas the second potential gives much more improved results at mediumand large J values, in reasonable agreement with the experimental data. For the line shifts which mainly arise in our calculation from theelectronic state dependence of the isotropic potential, their general trends with increasing J values can be well predicted, especially fromthe first potential. From the theoretical results, we have derived air-broadening and air-induced shift coefficients with an agreement com-parable to that obtained for O2–O2 and O2–N2. 2008 Elsevier Inc. All rights reserved.
Predoi-Cross A, Hambrook K, Keller R, Povey C, Schofield I, Hurtmans D, Over H, Mellau GC. Spectroscopic lineshape study of the self-perturbed oxygen A-band. Journal of Molecular Spectroscopy. 2008;248:85-110.Abstract
This paper reports accurate line positions, intensities, self-broadening, -shift and -line mixing coefficients for 56 rotational transitionsfrom multispectrum fits of low noise, high-resolution Fourier-transform spectra. The measured line intensities are within the statisticalspread of the previous measurements available in the literature—thus contributing to the efforts to measure the oxygen A-band intensitieswith an accuracy better than 1%. We determined the integrated band strength and Einstein A coefficient. Using our spectrum calibrationmethod we could clearly show for the first time that there is a meaningful statistical discrepancy in the frequency standards used in spec-troscopic studies for the oxygen A-band. We were able to explain how this discrepancy leads to two different sets of shifts reported in theliterature and demonstrate the need for precise frequency-type transition wavenumber measurements of the oxygen A-band transitions.We observed deviations from the conventional Voigt profile due to speed-dependent broadening and line mixing effects. Dicke narrowingwas observed on a selected group of spectra recorded at pressures between 98 and 337 Torr. The Dicke narrowed lineshapes were bestmodeled using a Galatry profile implemented using a fixed value for the velocity-changing collision rate. The weak line mixing coefficientswere determined from fits using the speed-dependent models. Exponential Power Gap (EPG) and Energy Corrected Sudden (ECS) scal-ing laws were used to calculate the self-broadening and self-line mixing coefficients. 2007 Elsevier Inc. All rights reserved.
2007
Predoi-Cross A, Unni AV, Heung H, Malathy Devi V, Chris Benner D, Brown LR. Line mixing effects in the ν2+ν3 band of methane. Journal of Molecular Spectroscopy. 2007;246:65-76.Abstract
This study provides the first direct experimental measurements of the off-diagonal relaxation matrix element coefficients for line mixingin air-broadened methane spectra for any vibrational band and the first off diagonal relaxation matrix elements associated with line mix-ing for pure methane in the m2 + m3 band of 12CH4. The speed-dependent Voigt profile with line mixing is used with a multispectrumnonlinear least squares curve fitting technique to retrieve the various line parameters from 11 self-broadened and 10 air-broadened spec-tra simultaneously. The room temperature spectra analyzed in this work are recorded at 0.011 cm1 resolution with the McMath-PierceFourier transform spectrometer located at the National Solar Observatory, Kitt Peak, Arizona. The off-diagonal relaxation matrix ele-ment coefficients of m2 + m3 transitions between 4410 and 4629 cm1 are reported for eighteen pairs with upper state J values between 2and 11. The observed line mixing coefficients for self broadening vary from 0.0019 to 0.0390 cm1 atm1 at 296 K. The measured linemixing coefficients for air broadening vary from 0.0005 to 0.0205 cm1 atm1 at 296 K. 2007 Elsevier Inc. All rights reserved.
Predoi-Cross A, Liu W, Holladay C, Unni AV, Schofield I, McKellar ARW, Hurtmans D. Line profile study of transitions in the 30012←00001 and 30013←00001 bands of carbon dioxide perturbed by air. Journal of Molecular Spectroscopy. 2007;246:98-112.Abstract
In this work we present a line profile study for air-broadened carbon dioxide transitions in the 30012‹00001 and 30013‹00001vibrational bands. The room temperature spectra were recorded at a resolution of 0.008 cm1 using a Fourier Transform spectrometer.The air-broadening, air-shift, and air-line mixing coefficients were derived from a simultaneous fitting of spectra using the Voigt modeland a Speed-Dependent Voigt lineshape model. The results obtained are consistent with other studies in addition to the theoreticallycalculated values. Exponential Power Gap (EPG) and Energy Corrected Sudden (ECS) scaling laws were used to calculate the relaxationmatrix elements.
Predoi-Cross A, Unni AV, Liu W, Schofield I, Holladay C, McKellar ARW, Hurtmans D. Line shape parameters measurement and computations for self-broadened carbon dioxide transitions in the 30012←00001 and 30013←00001 bands, line mixing, and speed dependence. Journal of Molecular Spectroscopy. 2007;245:34-51.Abstract
Transitions of pure carbon dioxide have been measured using a Fourier transform spectrometer in the 30012‹00001 and30013‹00001 vibrational bands. The room temperature spectra, recorded at a resolution of 0.008 cm1, were analyzed using the Voigtmodel and a Speed Dependent Voigt line shape model that includes a pressure dependent narrowing parameter. Intensities, self-inducedpressure broadening, shifts, and weak line mixing coefficients are determined. The results obtained are consistent with other studies inaddition to the theoretically calculated values. Exponential Power Gap (EPG) and Energy Corrected Sudden (ECS) scaling laws wereused to calculate the relaxation matrix elements. 2007 Elsevier Inc. All rights reserved.
2006
Predoi-Cross A, Hambrook K, Brawley-Tremblay M, Bouanich J-P, Smith MAH. Measurements and theoretical calculations of N2-broadening and N2-shift coefficients in the ν2 band of CH3D. Journal of Molecular Spectroscopy. 2006;235:35-53.Abstract
In this paper, we report measured Lorentz N2-broadening and N2-induced pressure-shift coefficients of CH3D in the m2 fundamentalband using a multispectrum fitting technique. These measurements were made by analyzing 11 laboratory absorption spectra recorded at0.0056 cm1 resolution using the McMath-Pierce Fourier transform spectrometer located at the National Solar Observatory on KittPeak, Arizona. The spectra were obtained using two absorption cells with path lengths of 10.2 and 25 cm. The total sample pressuresranged from 0.98 to 402.25 Torr with CH3D volume mixing ratios of 0.01 in nitrogen. We have been able to determine the N2 pres-sure-broadening coefficients of 368 m2 transitions with quantum numbers as high as J00 = 20 and K = 16, where K00 = K0 ” K (for a parallelband). The measured N2-broadening coefficients range from 0.0248 to 0.0742 cm1 atm1 at 296 K. All the measured pressure-shifts arenegative. The reported N2-induced pressure-shift coefficients vary from about 0.0003 to 0.0094 cm1 atm1. We have examined thedependence of the measured broadening and shift parameters on the J00, and K quantum numbers and also developed empirical expres-sions to describe the broadening coefficients in terms of m (m = J00, J00, and J00 + 1 in the QP-, QQ-, and QR-branch, respectively) and K.On average, the empirical expressions reproduce the measured broadening coefficients to within 4.7%. The N2-broadening and pressure-shift coefficients were calculated on the basis of a semiclassical model of interacting linear molecules performed by considering in addi-tion to the electrostatic contributions the atom–atom Lennard-Jones potential. The theoretical results of the broadening coefficients arein good overall agreement with the experimental data (8.7%). The N2-pressure shifts whose vibrational contribution is derived fromparameters fitted in the QQ-branch of self-induced shifts of CH3D, are also in reasonable agreement with the scattered experimental data(20% in most cases). 2005 Elsevier Inc. All rights reserved.
Predoi-Cross A, Brawley-Tremblay M, Brown LR, Devi MV, Benner CD. Multispectrum analysis of 12CH4 from 4100 to 4635cm−1: II. Air-broadening coefficients (widths and shifts). Journal of Molecular Spectroscopy. 2006;236:201-215.Abstract
Room temperature Lorentz air-broadened halfwidth and pressure-induced air-shift coefficients were measured for 1011 transitions inthe octad region of methane between 4100 and 4635 cm1. These measurements were made by analyzing 10 laboratory absorption spec-tra recorded at 0.011 cm1 resolution using the McMath–Pierce Fourier transform spectrometer located at the National Solar Observa-tory on Kitt Peak, Arizona. The spectra were obtained using two absorption cells with path lengths of 2.05 and 150 cm. The total samplepressures ranged from 99 to 400 torr with CH4 volume mixing ratios of 0.01 in dry air. The spectral line parameters were retrieved using amultispectrum nonlinear least squares technique. Transitions belonging to five bands of the octad polyad were observed, namely m2 +2m4,m1 + m4, m3 + m4,2m2 + m4, and m2 + m3. The numbers of measurements by bands are: 33 for m2 +2m4, 180 for m1 + m4, 635 for m3 + m4, 33 for2m2 + m4, and 130 for m2 + m3. Transitions with rotational quantum number J up to 16 are included in the analysis. The measured widthand shift coefficients vary according to the tetrahedral symmetry species and the rotational quantum numbers of the transitions. Theretrieved parameters from this study are compared with prior results, in part to estimate absolute accuracy and determine the extentof vibrational dependence of widths and shifts. 2006 Elsevier Inc. All rights reserved.
Predoi-Cross A, Hambrook K, Brawley-Tremblay S, Bouanich J-P, Devi MV, Smith MAH. Room-temperature broadening and pressure-shift coefficients in the ν2 band of CH3D–O2: Measurements and semi-classical calculations. Journal of Molecular Spectroscopy. 2006;236:75-90.Abstract
We report measured Lorentz O2-broadening and O2-induced pressure-shift coefficients of CH3D in the m2 fundamental band. Using amultispectrum fitting technique we have analyzed 11 laboratory absorption spectra recorded at 0.011 cm 1 resolution using theMcMath–Pierce Fourier transform spectrometer, Kitt Peak, Arizona. Two absorption cells with path lengths of 10.2 and 25 cm wereused to record the spectra. The total sample pressures ranged from 0.98 to 339.85 Torr with CH3D volume mixing ratios of 0.012 inoxygen. We report measurements for O2 pressure-broadening coefficients of 320 m2 transitions with quantum numbers as high asJ00 = 17 and K = 14, where K00 = K0 ” K (for a parallel band). The measured O2-broadening coefficients range from 0.0153 to0.0645 cm 1 atm 1 at 296 K. All the measured pressure-shifts are negative. The reported O2-induced pressure-shift coefficients vary fromabout 0.0017 to 0.0068 cm 1 atm 1. We have examined the dependence of the measured broadening and shift parameters on the J00,and K quantum numbers and also developed empirical expressions to describe the broadening coefficients in terms of m (m = J00, J00,and J00 + 1 in the QP-, QQ-, and QR-branch, respectively) and K. On average, the empirical expressions reproduce the measured broadeningcoefficients to within 4.4%. The O2-broadening and pressure shift coefficients were calculated on the basis of a semiclassical modelof interacting linear molecules performed by considering in addition to the electrostatic contributions the atom–atom Lennard-Jonespotential. The theoretical results of the broadening coefficients are generally larger than the experimental data. Using for the trajectorymodel an isotropic Lennard-Jones potential derived from molecular parameters instead of the spherical average of the atom–atom model,a better agreement is obtained with these data, especially for |m| 6 12 values (11.3% for the first calculation and 8.1% for the secondcalculation). The O2-pressure shifts whose vibrational contribution are either derived from parameters fitted in the QQ-branch of selfinducedshifts of CH3D or those obtained from pressure shifts induced by Xe in the m3 band of CH3D are in reasonable agreement withthe scattered experimental data (17.0% for the first calculation and 18.7% for the second calculation). 2005 Elsevier Inc. All rights reserved.
2005
Predoi-Cross A, Hambrook K, Brawley-Tremblay M, Bouanich J-P, Malathy Devi V, Benner CD, Brown LR. Measurements and theoretical calculations of self-broadening and self-shift coefficients in the ν2 band of CH3D. Journal of Molecular Spectroscopy. 2005;234:53-74.Abstract
In this paper, we report measured Lorentz self-broadening and self-induced pressure-shift coefficients of 12CH3Dinthe m2 fun-damental band (m0  2200 cm1). The multispectrum fitting technique allowed us to analyze simultaneously seven self-broadenedabsorption spectra. All spectra were recorded at the McMath-Pierce Fourier transform spectrometer of the National Solar Obser-vatory (NSO) on Kitt Peak, AZ with an unapodized resolution of 0.0056 cm1. Low-pressure (0.98–2.95 Torr) as well as high-pres-sure (17.5–303 Torr) spectra of 12C-enriched CH3D were recorded at room temperature to determine the pressure-broadeningcoefficients of 408 m2 transitions with quantum numbers as high as J00 = 21 and K = 18, where K00 = K0 ” K (for a parallel band).The measured self-broadening coefficients range from 0.0349 to 0.0896 cm1 atm1 at 296 K. All the measured pressure-shiftsare negative. The reported pressure-induced self-shift coefficients vary from about 0.004 to 0.008 cm1 atm1.We have examinedthe dependence of the measured broadening and shift parameters on the J00, and K quantum numbers and also developed empiricalexpressions to describe the broadening coefficients in terms of m (m = J00, J00, and J00 + 1 in the QP-, QQ-, and QR-branch, respec-tively) and K. On average, the empirical expressions reproduce the measured broadening coefficients to within 3.6%. A semiclassicaltheory based upon the Robert–Bonamy formalism of interacting linear molecules has been used to calculate these self-broadeningand self-induced pressure-shift coefficients. In addition to the electrostatic interactions involving the octopole and hexadecapolemoments of CH3D, the intermolecular potential includes also an atom–atom Lennard–Jones model. For low K (K 6 3) with|m| 6 8 the theoretical results of the broadening coefficients are in overall good agreement (3.0%) with the experimental data.For transitions with K approaching |m|, they are generally significantly underestimated (8.8%). The theoretical self-induced pressureshifts, whose vibrational contribution is derived from results in the QQ-branch, are generally smaller in magnitude than the exper-imental data in the QP-, and QR-branches (15.2%). 2005 Elsevier Inc. All rights reserved.
Predoi-Cross A, Brown LR, Devi MV, Brawley-Tremblay M, Benner CD. Multispectrum analysis of 12CH4 from 4100 to 4635cm−1: 1. Self-broadening coefficients (widths and shifts). Journal of Molecular Spectroscopy. 2005;232:231-246.Abstract
The Lorentz self-broadening (halfwidths) and self-induced pressure-shift coefficients were measured for the first time in the octadregion of methane. All spectra were recorded at 0.011 cm 1 resolution using the McMath–Pierce Fourier transform spectrometerlocated at the National Solar Observatory on Kitt Peak, Arizona. 12C-enriched CH4 gas samples at room temperature were used,and high signal-to-noise ratios of 2000:1 were achieved. The multispectrum nonlinear least squares fitting technique enabled us to fitsimultaneously a total of 10 high-resolution laboratory absorption spectra consisting of six self-broadened and four air-broadenedspectra. In this paper, we report the self-broadened widths and self-induced pressure shift coefficients for 1423 transitions belongingto five bands with a maximum J of 16. The numbers of measurements by bands are: 71 for m2 + 2m4, 202 for m1 + m4, 824 for m3 + m4,58 for 2m2 + m4, and 268 for m2 + m3. The observed widths varied from 0.045 to about 0.090 cm 1 atm 1 at 296 K. The measuredpressure-shift coefficients had values extending from about 0.020 to 0.005 cm 1 atm 1 at 298.3 ± 1.2 K. The results obtainedfor the broadening coefficients in the various bands were compared with each other and with measurements reported in the literaturefor other methane bands. 2005 Elsevier Inc. All rights reserved.
Devi MV, Benner CD, Smith MAH, Rinsland CP, Predoi-Cross A, Sharpe SW, Sams RL, Boulet C, Bouanich JP. A multispectrum analysis of the ν2 band of H12C14N: Part I. Intensities, broadening, and shift coefficients. Journal of Molecular Spectroscopy. 2005;231:66-84.Abstract
Absolute intensities, self- and air-broadening coefficients, self- and air-induced shift coefficients and their temperature dependenceshave been determined for lines belonging to the P- and R-branches of the m2 band of H12C14N centered near 712 cm 1. Infraredspectra of HCN in the 14-lm region were obtained at high resolution (0.002–0.008 cm 1) using two different Fourier transformspectrometers (FTS), the McMath-Pierce FTS at the National Solar Observatory on Kitt Peak and the Bruker IFS 120HR FTS atthe Pacific Northwest National Laboratory. Spectra were recorded with 99.8% pure HCN as well as lean mixtures of HCN in air atvarious temperatures ranging between +26 and 60 C. A multispectrum nonlinear least squares technique was used to fit selectedintervals of 36 spectra simultaneously to obtain the line positions, intensities, broadening, and shift parameters. The measured lineintensities were analyzed to determine the vibrational band intensity and the Herman–Wallis coefficients. The measured self-broadeningcoefficients vary between 0.2 and 1.2 cm 1 atm 1 at 296 K, and the air-broadening coefficients range from 0.08 to0.14 cm 1 atm 1 at 296 K. The temperature dependence exponents of self-broadening range from 1.46 to 0.12 while the correspondingexponents for air broadening vary between 0.58 and 0.86. The present measurements are the first known determinationof negative values for the temperature dependence exponents of HCN-broadening coefficients. We were able to support our selfbroadeningmeasurements with appropriate theoretical calculations. Our present measurements are compared, where possible, withprevious measurements for this and other HCN bands, as well as the parameters that are included in the 2000 and 2004 editions ofthe high-resolution transmission (HITRAN) database. 2005 Elsevier Inc. All rights reserved.
Mantz AW, Malathy Devi V, Chris Benner D, Smith MAH, Predoi-Cross A, Dulick M. A multispectrum analysis of widths and shifts in the 2010–2260cm−1 region of 12C16O broadened by Helium at temperatures between 80 and 297K. Journal of Molecular Structure. 2005;742:99-110.Abstract
Lorentz pressure-broadening and pressure-induced shift coefficients along with their temperature dependences have been determined forover forty P- and R-branch transitions in the fundamental band of 12C16O broadened with helium. A total of nineteen spectra recorded atvarious temperatures (C24 to K194 8C) in the 2010–2260 cmK1 spectral region were analyzed simultaneously using a multispectrumnonlinear least squares fitting technique. The spectra were recorded with the McMath-Pierce Fourier transform spectrometer located at theNational Solar Observatory on Kitt Peak. Present results are compared with similar measurements reported recently.q 2005 Elsevier B.V. All rights reserved.
Bouanich J-P, Predoi-Cross A. Theoretical calculations for line-broadening and pressure-shifting in the fundamental and first two overtone bands of CO–H2. Journal of Molecular Structure. 2005;742:183-190.Abstract
The line broadening and shift coefficients for CO–H2 in the fundamental and first two overtone bands are modeled using semi-classical calculations based on the Robert–Bonamy formalism and two isotropic and anisotropic intermolecular potentials. These potentials involve electrostatic contributions and (a) the atom–atom Lennard-Jones model, or (b) the Tipping–Herman model with adjustable parameters in order to fit the broadening coefficients. For the line shifts, which appear to arise only from vibrational dephasing effects, different values for the relative dependence of the attractive and repulsive parts of the isotropic potential are used. The calculated broadening and shiftparameters are then compared with experimental results available in the literature. This comparison shows a reasonable agreement of the broadening parameters and a less satisfactory agreement of the line shifts for which the experimental data are on the whole rather inaccurate.q 2005 Elsevier B.V. All rights reserved.
Predoi-Cross A, Baranov YI. Lineshape modeling of inter-branch intensity transfer in the 2000←0110, 1110←0000 and 1220←0110 Q-branches of carbon dioxide. Journal of Molecular Structure. 2005;742:77-82.Abstract
An adjustable band shape calculation model based on the strong collision approximation with inter-branch coupling has been applied to predict line mixing in the 2000)0110, 1220)0110 and in the 1110)0000 Q-branches of carbon dioxide. In this approach, the band shape is calculated using an adjustable parameter to account for line mixing effects, in addition to the usual set of spectral parameters used to describe the band shape. The good quality of the model is proven by comparisons with experimental spectra recorded at room temperature over a widepressure range (1–21 atm). All spectra were recorded using a Fourier transform spectrometer and 25 cm long temperature controlled cell. Thevalues obtained for the adjustable parameter for the three Q-branches are discussed.q 2005 Elsevier B.V. All rights reserved.
2004
Predoi-Cross A, May AD, Vitcu A, Drummond JR, Hartmann JM, Boulet C. Broadening and line mixing in the 20 (0)0<--01 (1)0, 11 (1)0<--00 (0)0 and 12 (2)0<--01 (1)0 Q branches of carbon dioxide: experimental results and energy-corrected sudden modeling. J Chem Phys [Internet]. 2004;120:10520-9. Publisher's VersionAbstract
Using both a difference frequency spectrometer and a Fourier transform spectrometer, we have measured transitions in the 12 (2)0&lt;--01 (1)0 band of carbon dioxide at room temperature and pressures up to 19 atm. The low-pressure spectra were analyzed using a variety of standard spectral profiles, all with an asymmetric component to account for weak line mixing. For this band, we have been able to retrieve experimental line strengths and the broadening and weak mixing parameters. In this paper we also compare the suitability of the energy-corrected sudden model to predict mixing in the two previously measured Q branches 20 (0)0&lt;--01 (1)0, the 11 (1)0&lt;--00 (0)0, and the present Q branch of pure CO(2), all at room temperature.
Malathy Devi V, Predoi-Cross A, Chris Benner D, Smith MAH, Rinsland CP, Mantz AW. Self- and H2-broadened width and shift coefficients in the 2←0 band of 12C16O: revisited. Journal of Molecular Spectroscopy. 2004;228:580-592.Abstract
Room temperature values for self-broadened and hydrogen-broadened Lorentz halfwidth coefficients, and self and hydrogenpressure-induced shift coefficients have been measured for transitions with rotational quantum number m ranging between )24 and24 in the 2 0 band of 12C16O. The spectra were recorded with the McMath–Pierce Fourier transform spectrometer located at theNational Solar Observatory on Kitt Peak. The analysis was performed using a multispectrum nonlinear least squares technique. Wehave compared our results with similar measurements published recently. 2004 Elsevier Inc. All rights reserved.
Predoi-Cross A, Hnatovsky C, Strong K, Drummond JR, Chris Benner D. Temperature dependence of self- and N2-broadeningand pressure-induced shifts in the 3←0 band of CO. Journal of Molecular Structure. 2004;695-696:269-286.Abstract
A variable-temperature single-pass absorption gas cell with an optical pathlength of 147.5 cm was designed and built for spectroscopicmeasurements of gases of atmospheric interest. The cell is optically matched to a Bomem DA8.3 Fourier transform spectrometer. Aheating/cooling system enveloping the cell, used together with a Neslab ULT-80 thermal bath, allows spectroscopic studies of gas samples attemperatures ranging from 205 to 350 K and at pressures up to 1 atm. Tests of the optical, thermal, and vacuum operation of the system wereperformed. Spectra of the 3ˆ0 vibrational–rotational band of carbon monoxide were recorded from 225 to 348 Kand used to determine therotational gas temperatures. These results were compared with values obtained using thermocouples, in order to assess the thermalperformance of the new system. A second temperature-controlled cell 25-cm long, able to withstand pressures up to 30 atm, was also used torecord CO spectra. We have recorded high-resolution FTIR spectra of CO and CO perturbed by N2 at temperatures from 295 to 348 K. Thespectra were analyzed to determine pressure broadening and pressure-induced shift coefficients, along with their temperature dependence forseveral transitions in the second overtone band of CO. The results, especially for self-broadening, are in excellent agreement with otherrecent measurements reported in the literature.q 2004 Elsevier B.V. All rights reserved.
2003
Brault JW, Brown LR, Chackerian C, Freedman R, Predoi-Cross A, Pine AS. Self-broadened 12C16O line shapes in the v=2←0 band. Journal of Molecular Spectroscopy. 2003;222:220-239.Abstract
Precise intensities, self-broadenings and shifts have been obtained for the 12C16O v ¼ 2 0 band from simultaneous fits of lownoise,high-resolution Fourier-transform spectra at pressures from 27 to 80 kPa (200–600 Torr). Observed line shapes exhibit deviationson the order of 1% from the conventional Voigt profile, primarily due to speed-dependent broadening and secondarily toline mixing. Dicke narrowing is reduced by over an order-of-magnitude from the diffusion value, presumably because of correlationsbetween velocity- and phase-changing collisions. 2003 Elsevier Inc. All rights reserved.
Brown LR, Chris Benner D, Champion JP, Devi VM, Fejard L, Gamache RR, Gabard T, Hilico JC, Lavorel B, Loete M, et al. Methane line parameters in HITRAN. Journal of Quantitative Spectroscopy and Radiative Transfer. 2003;82:219-238.Abstract
Two editions of the methane line parameters (line positions, intensities and broadening coe
2000
Predoi-Cross A, Bouanich JP, Benner CD, May AD, Drummond JR. Broadening, shifting, and line asymmetries in the 2]0 bandof CO and CO–N2 : Experimental results and theoretical calculations. Journal of Chemical Physics. 2000;113.Abstract
We have measured the room temperature, widths, pressure shifts, and line asymmetry coefficientsfor many transitions of the first overtone band of CO and CO perturbed by N2 . The broadeningcoefficients were obtained with an accuracy of about 1%. The pure CO profiles have been fitted bya Voigt profile while the CO–N2 spectral profiles have been fitted with a Lorentz and an empiricalline shape model (HCv) that blends together a hard collision model and a speed-dependent Lorentzprofile. In addition to the Voigt, Lorentz, and HCv models, we have added a dispersion profile toaccount for weak line mixing. The line broadening and shift coefficients are compared tosemiclassical calculations employing a variety of intermolecular interactions. The line asymmetryresults are compared to line mixing calculations based on the energy corrected sudden ~ECS! model. The results indicate that effects other than line mixing also contribute to the measured lineasymmetry. © 2000 American Institute of Physics. @S0021-9606~00!01425-2#
Predoi-Cross A, Luo C, Berman R, Drummond JR, May AD. Line strengths, self-broadening, and line mixingin the 20 0 0 - 01 1 0 „S-P…Q branch of carbon dioxide. Journal of Chemical Physics. 2000;112.Abstract
Using a difference frequency spectrometer we have measured the Q(2) to Q(38) 2000Ã0110,SÃP transitions of carbon dioxide at 296 K and pressures up to 15 kPa. These low pressure spectrawere analyzed using both the Voigt model, and an empirical line shape that blends together a hardcollision model and a speed dependent Lorentzian profile. The broadening coefficients wereobtained with an accuracy of 1% or better. The low density or first order low pressure line mixingparameters were also determined. We have compared both our measured low pressure line-mixingparameters and the complete band spectrum at high pressures with those predicted by a relaxationmatrix calculated from an EPG fitting law. Spectra at the highest pressures were recorded using boththe difference frequency spectrometer and an FTIR spectrometer, the temperature for the latterexperiments being 303 K. The vibrational band intensity and linear pressure shift of the branch asa whole were also measured. © 2000 American Institute of Physics. @S0021-9606~00!01519-1#
1999
Predoi-Cross A, Luo C, Sinclair PM, Drummond JR, May AD. Line Broadening and the Temperature Exponent of the Fundamental Band in CO–N2 Mixtures. Journal of Molecular Spectroscopy. 1999;198.Abstract
We have measured the width, G, of many P and R lines of the fundamental vibration–rotation band of CO perturbed by N2at 348 K and pressures of about 50 kPa. We have also extended the measurements made earlier at room temperature. Thebroadening coefficients, g 5 G/pressure, were obtained with an accuracy of 0.3% by fitting with a Lorentzian, a Voigt, andan empirical lineshape model that blends together a hard-collision model and a speed-dependent Lorentzian profile. In all casesthe results are represented by an empirical exponential power law polynomial in the line number, m. Combining the data atthe two temperatures yields the exponent n in the scaling law g(T1)/g(T2) 5 (T1/T2)2n, as a function of line number. Thebroadening coefficients and the variation of the temperature exponent line number are compared with theory. In addition, theline-mixing parameters are also reported at 348 and 301 K.
Luo C, Berman R, Predoi-Cross A, Drummond JR, May AD. Lineshifts in the Fundamental Band of CO: Confirmation of Experimental Results for N2 and Comparison with Theory. Journal of Molecular Spectroscopy. 1999;196:290-295.Abstract
We have used a three-channel version of a tunable difference frequency laser spectrometer to measure the collisionallyinduced lineshifts at room temperature for 26 lines of the fundamental band of CO perturbed by nitrogen. Each lineshift wasobtained directly by comparing the line center positions of two simultaneous recordings, one for a pressure-shifted line, andthe other for the same line in pure CO line at very low pressure. The experimental results are found to be in complete agreementwith earlier measurements and confirm that shifts as small as 3 MHz may be measured in such a system. Our results arecompared with theoretical calculations. The part of the shifting coefficient antisymmetric with respect to a change in sign ofthe line number m, is in disagreement with the calculations. © 1999 Academic Press
1998
Perrin A, Flaud J-M, Predoi-Cross A, Winnewisser M, Winnewisser BP, Mellau G, Lock M. New High-Resolution Analysis of the n3 , n4 , and n6 Bands of D2COMeasured by Fourier Transform Spectroscopy. Journal of Molecular Spectroscopy. 1998;187:61-69.Abstract
A reanalysis of the n3 , n4 , and n6 interacting bands of D2CO has been carried out in the region 850–1250 cm01 using high-resolution Fourier transform spectra recorded at Giessen. As compared to the previous study of these bands (1987, K. Nakagawa, R. H. Schwendeman, and J. W. C. Johns, J. Mol. Spectrosc. 122, 462–476) higher J and Ka transitions were assigned for the three bands, leading to a better determination of the upper state constants. The £3  1, £4  1, and £6  1 experimental energy levels were introduced in a least-squares fit calculation together with the microwavemeasurements available in the literature in order to obtain the upper state parameters (band centers, rotational and coupling constants) . In this calculation, which allowed us to reproduce both the infrared and the microwave measurements to within their experimental accuracies, the A-, B-, and C-type Coriolis interactions involving the rotational levels belonging to the £4  1 and £6  1, £3  1 and £4  1, and £3  1 and £6  1 interacting states respectively were explicitly taken into account. Finally, from the intensities, a new determination of the relative values of the q3 , q4 , andq6 first derivatives of the D2CO dipole moment was performed. q 1998 Academic Press
Predoi-Cross A, Lees RM, Johns JWC. Fourier Transform Infrared Spectroscopy and Vibrational Coupling in the OH-Bending Band of 13CH3OH. Journal of Molecular Spectroscopy. 1998;191:348-361.Abstract
We present in this work a high-resolution Fourier transform infrared study of the OH-bending vibrational band of 13have investigated the 1070–1400 cm1 spectral region at 0.002 cm1 resolution using the modified Bomem DA3.002 FourierCH3 1338 cm1 transform spectrometer at the Steacie Institute for Molecular Sciences at the National Research Council of Canada in Ottawa. Thisstudy has led to (i) determination of excited-state J(J  1) subband expansion coefficients and (ii) characterization of a variety ofinteractions coupling the different vibrational modes, notably a strong Fermi resonance between the OH bend and the torsionallyexcited CH3 have been fitted to J(J  1) power-series expansions in order to obtain the subband origins and the state-specific energy expansioncoefficients for both the OH-bending and excited torsional CH3 and the first excited torsional CH3 asymmetry splitting of the (n K)v (122)runusual behavior, but a quantitative analysis of the vibrational coupling is restricted by limited knowledge of the unperturbedpositions of the interacting levels. All these interactions provide relaxation channels for intramolecular vibrational redistributionamong the lower vibrational modes in 13CH3OH-bending state display an inverted pattern compared to the ground state. © 1998 Academic Press
Predoi-Cross A, Mellau GC, Lees RM, Winnewisser BP. Fourier Transform Infrared Spectroscopy of the First CO-Stretch Overtone Band of 13CH3OH. Journal of Molecular Spectroscopy. 1998;189:144-152.Abstract
This paper presents a high-resolution Fourier transform infrared study of the first CO-stretch overtone band of13CH3OH. The spectrum has been recorded at the Justus-Liebig University, Gießen, Germany on their Bruker IFS 120HR Fourier transform spectrometer. We have assigned parallel subbands in the torsional state n  0 for K values up to6. Each individual subband has been fitted to a J(J / 1) power series expansion in order to obtain the subband originand the state-specific energy expansion coefficients for the first CO-stretch overtone state. The average rotational constantB in the CO-stretch £CO  2 state was found to be 0.768 cm01 , forming a smooth series with that of 0.777 cm01 obtainedin the £CO  1 state and the ground state value of 0.787 cm01 . Modeling of the excited state torsion–vibration energylevel structure derived from the subband origins is then discussed and molecular parameters in the £CO  2 state areproposed. The value obtained for the barrier height to internal rotation is 377.06 { 0.52 cm01 , nearly indistinguishablefrom the value 378.65 cm01 reported for the CO-stretch £CO  1 state. The vibrational energy is found to be 2020.9 {1.4 cm01 . The harmonic wavenumber for the CO-stretch vibration in 13CH3OH was calculated to be v  1029.9 cm01 .The anharmonicity constant of this vibration is vx  6.5 cm01 , giving x  6.3 1 1003 . We have also observedasymmetry-induced K doubling for the subbands of A symmetry for K values from 1 to 3 at sufficiently high J values.The size of the splitting coefficients is similar to those observed for the CO-stretch fundamental (14) , with the exception of those for the K  3A doublet, where the observed splitting is about 18% larger than that for the ground and COstretch£CO  1 states. 1998 Academic Press
1997
Predoi A, Lees RM, Johns JWC. Fourier transform spectrum of the in-plane CH3-rocking fundamentaland vibrational coupling in C-13 methanol. Journal of Chemical Physics. 1997;107.Abstract
The Fourier transform infrared spectrum of the in-plane CH3-rocking fundamental of 13CH3OH has been investigated at 0.002 cm21 resolution. The rocking band is principally of parallel character and has a double-peaked Q branch and relatively wide spread subbands indicative of a substantialchange in torsional barrier height. All A subbands from K50 to 11 and all but one E subband fromK50 to 9 have been assigned in the n50 torsional state and fitted to J(J11) power-seriesexpansions to obtain the subband origins and excited-state energy structure. The effects ofvibrational interactions between the CH3-rocking and CO-stretching modes are prominent in thespectrum. Coriolis coupling between rocking (K21) and CO-stretching K levels is observable forK&gt;6, and makes significant contributions to the subband origins and effective B values. SeveralJ-localized perturbations due to level-crossing resonances with CO-stretch states have beenobserved and characterized. Two reported strong far-infrared laser lines optically pumped by the10R(26) CO2 laser line have been found to arise through such a DK53 level-crossing resonance.Modeling of the rocking-state torsion-K-rotation energies yields a height of V3 r 5469.2(38) cm21for the torsional potential barrier, a 26% increase over the ground state. The asymmetry K-doublingpattern in the excited state is qualitatively consistent with this barrier for K52 to 4, but the K55 rocking substate displays strongly enhanced splitting. © 1997 American Institute of Physics.@S0021-9606~97!01929-6#
Predoi-Cross A, Lees RM, Lichau H, Winnewisser M, Drummond JR. The millimeter wave spectrum of CH3OH in the 199-165 GHz spectral range. International Journal of Infrared and Millimeter Waves. 1997;18.Abstract
The rotational millimeter-wave spectrum of CH318OH has been revisited, and 162 transitions of both a- and b-types have been measured in the 119-165 GHz spectral range. The spectrum was recorded using thefrequency-modulated millimeter-wave spectrometer at the/ustus-Liebig-Universit~it in Giegen. The CH318OH transition assignments were basedon energy levels obtained from the far-infrared analysis of S. Zhao (Ph.D.thesis, University of New Brunswick, 1993) using the "Ritz" program ofG. Moruzzi et al. (J. Mol. Spectrosc. 167, 156 (1994)) for direct energylevel fitting. The relatively low residuals between calculated and observed frequencies highlight the good quality of the results from this program. The newly measured transitions combined with those existent in the literature have been included in least-squares fits to improve the set of rotational,torsional and centrifugal distortion constants for O-18 methanol.
Predoi-Cross A, Xu L-H, Walsh MS, Lees RM, Winnewisser M, Lichau H. New Measurements and Assignments in the Millimeter-Wave Spectrum of CD3OH. Journal of Molecular Spectroscopy. 1997;188:94-101.Abstract
The ground state rotational spectrum of CD3OH has been revisited in the millimeter-wave range. A total of 216transition frequencies have been measured and assigned in the 117–179 GHz spectral range, including about 40 transitionspreviously reported. The spectrum was recorded at the Justus–Liebig University in Gießen, Germany using a frequencymodulated millimeter-wave spectrometer. The assignments for the CD3OH transitions were predicted based on energylevels calculated using preliminary results of the global fit of microwave, millimeter-wave, and far-infrared data ofWalsh et al. (Paper FC04 presented at the 52nd International Symposium of Molecular Spectroscopy, Columbus, OH,1997) . The new measurements have substantially enlarged the accurate millimeter-wave component of the data setavailable for the global fit and have allowed Walsh et al. to obtain significant improvement in the CD3OH molecularparameters ( J. Mol. Spectrosc. 188, 85–93, 1998) . The low residuals between observed and calculated frequencieshighlight the quality of the global fit results. 1998 Academic Press
1996
Lees RM, Mukhopadhyay I, Predoi A, Lewis-Bevan W, Johns JWC. Fourier transform spectroscopy of torsionally excited C-13 methanolin the CO-stretching band. Journal of Chemical Physics. 1996;105.Abstract
Torsionally excited n51 and n52 subbands of the CO-stretching fundamental have been assignedin the Fourier transform infrared spectrum of 13CH3OH recorded at a resolution of 0.002 cm21. Forthe n51 torsional state, subbands with K values up to 7 have been identified for A torsionalsymmetry and up to 5 for E symmetry. For n52, four subbands have so far been assigned. Subbandorigins have been obtained by fitting the observed wave numbers to J(J11) power-seriesexpansions. The expansion parameters represent the data compactly to close to the experimentaluncertainty in the absence of line blending or perturbations. Significant downshifting of the n51origins is observed, correlated closely with proximity to the n50 OH-bending state. J-localizedperturbations have been observed and characterized for several subbands. Two of the far-infraredlaser lines optically pumped by the 10R~14! CO2 laser line have been assigned. © 1996 AmericanInstitute of Physics. @S0021-9606~96!01029-X#
1995
Predoi A, Lees RM, Xu L-H. Far infrared laser assignments and predictions for CO-stretching and CH3-rocking states of optically pumped 13CH3OH. Infrared Physics and Technology. 1995;37:351-366.Abstract
High-resolution Fourier transform studies of the CO-stretching and CH3-rocking bands of 13CH3OH have beenapplied to the assignment of far-infrared (FIR) laser transitions optically pumped by CO2 infrared (IR) lasers. Theassignments are based on spectroscopic identification of the IR pump transitions at the reported offsets from the CO2laser lines and agreement between the FIR laser wavenumbers and values calculated from IR/FIR combination-looprelations. Wavenumbers are also predicted for further potential new FIR laser lines in transition systems that couldbe pumped by CO2 and ~3CO2 cw and waveguide lasers.