Knowledge Bank

Fourier transform spectra have been recorded at $0.002cm-1$ resolution for the $\mathrm{<mrow\; data-mjx-texclass="ORD">13</mrow>}CH3OH$ isotopomer of methanol in the region from $900-1100cm-1$, covering the strong CO-stretching band and the much weaker in-plane $CH3$ rocking band. Analysis of the rocking band has led to the assignment of a number of optically-pumped far-infrared (FIR) laser line to transition within this band. As well, further results for FIR laser lines pumped in the CO-stretching band have been obtained. The transition and energy level system identifications have been checked in most case by closed-loop combination difference relations utilizing our infrared data plus FIR spectra of the torsion-rotation subbands in the ground vibrational state. Preliminary analysis of the assigned subbands of the $CH3$ rocking fundamental indicates significant change in the torsion-rotation energy level structure compared to the ground state, for which one interpretation is a substantially increased effective barrier height $V3$ in the rocking mode.