IR and FTMW-IR spectroscopy and vibrational relaxation pathways in the CH stretch region of CH3OH and CH3OD.

Infrared spectra of jet-cooled CH3OD and CH3OH in the CH stretch region are observed by coherence-converted population transfer Fourier transform microwave-infrared (CCPT-FTMW-IR) spectroscopy (E torsional species only) and by slit-jet single resonance spectroscopy (both A and E torsional species, CH3OH only). Twagirayezu et al. reported the analysis of ν3 symmetric CH stretch region (2750–2900 cm–1; Twagirayezu et al. J. Phys. Chem. A2010, 114, 6818), and the present work addresses the more complicated higher frequency region (2900–3020 cm–1) containing the two asymmetric CH stretches (ν2 and ν9). The additional complications include a higher density of coupled states, more extensive mixing, and evidence for Coriolis as well as anharmonic coupling. The overall observed spectra contain 17 interacting vibrational bands for CH3OD and 28 for CH3OH. The sign and magnitude of the torsional tunneling splittings are deduced for three CH stretch fundamentals (ν3, ν2, ν9) of both molecules and are compared to a mo...