Fourier transform spectroscopy of CH3OH: rotation–torsion–vibration structure for the CH3-rocking and OH-bending modes

Rotation–torsion–vibration term-value mapping for CH3OH: Torsion-mediated doorways and corridors for intermode population transfer

“…The spectra have been described previously in [6] and [7] and the reader is referred to those reports for more specific details. In the linelist in the Supplementary data, the transmittances are labeled as OttA for the NRC spectrum recorded at 13.5 Pa pressure and 2.0 m path, as OttB for the NRC spectrum at 100 Pa pressure and 2.0 m path, and as Gies for the Giessen spectrum recorded at 25 Pa pressure and 16.3 m path [7].…”

“…The spectra have been described previously in [6] and [7] and the reader is referred to those reports for more specific details. In the linelist in the Supplementary data, the transmittances are labeled as OttA for the NRC spectrum recorded at 13.5 Pa pressure and 2.0 m path, as OttB for the NRC spectrum at 100 Pa pressure and 2.0 m path, and as Gies for the Giessen spectrum recorded at 25 Pa pressure and 16.3 m path [7]. Recent precise sub-Doppler CO 2 -laser/microwave-sideband Lamb-dip measurements for CH 3 OH [12][13][14]17,24] showed that our earlier calibration in the 10 lm region [6] should be updated by dividing the reported wavenumbers by a factor of 1.000000122, and our line list in the Supplementary material has had that correction applied for the Ottawa spectra in the 930-1230 cm À1 region.…”

“…In our program, we have been analyzing rotationally resolved Fourier transform infrared (FTIR) spectra of CH 3 OH in the 930-1650 cm À1 region to investigate the rotation-torsion-vibration (R-T-V) energy manifold of the CO-stretching, CH 3 -rocking, OH-bending and CH 3 -deformation vibrational modes along with their torsional combinations [1][2][3][4][5][6][7]. By mapping the upper-state term values as a function of the J-rotational quantum number, we obtain a vivid and detailed picture of the energy structure that exposes a network of local resonances and near degeneracies interlinking the different modes and giving rise to a variety of spectral perturbations.…”

“…Since then, the CO stretch has been explored in great detail by a variety of high-resolution techniques, and studies have also been extended to other vibrational modes and isotopic species. Results up to 1995 for CH 3 OH were reviewed in a monograph by Moruzzi et al [10], and a number of further studies have since been reported (see [1][2][3][4][5][6][7] and [11][12][13][14][15][16][17] for example, plus references therein). In their book, in addition to extensive tables of rotation-torsion energies for the ground vibrational state, Moruzzi et al also presented term values for many excited m 8 CO-stretching substates as well as several substates of the m 7 in-plane CH 3 -rocking mode [10].…”

“…As noted in [7], although the torsion-vibration identities of the upper states of a number of the subbands are not yet clearly established, the positions of the upper energy levels can still be accurately determined by adding known ground-state energies [10] to the observed transition wavenumbers. Mapping of these upper term values then gives an informative picture of the locations of the local resonances and near-degeneracies occurring among the various torsionvibration substates, and adds considerable insight into some of the spectral puzzles that have been encountered.…”