Spectroscopic lineshape study of the self-perturbed oxygen A-band


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.


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.