Fourier transform synchrotron spectroscopy of torsional and CO-stretching bands of CH317OH

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.

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