Knowledge Bank

The low frequency vibrational modes and the torsion-rotation spectrum of methanol have been observed between $550cm-1$ and $1100cm-1$ using a 3 meter Ebert type, grating spectrometer with a resolution of about $0.1cm-1$. In the perpendicular type torsion-rotation transitions many individual P and R branch lines have been observed, in addition to the rather broad Q branches. This proved very advantageous in analysing the spectrum as will appear in the following paper by Y. Y. Kwan and D. M. Dennison. Most of the low frequency vibrational bands of the molecules, $CH3OH,CH3OD$, and $CD3OH$ show unusual splittings, comparable to the line spacing in the P and R branches. In particular the Q branch of $CH3OD$, for the O-D deformation, is split into many peaks. Some of the fine structure of the bands can be analyzed in terms of ``hot'' bands involving excited states of the torsional oscillation. Values of B and D for the ground and first excited states have been determined. The positions of the vibrational bands of the several isotopic molecules are also of interest since they have a bearing on the problem of the O-H deformation of $CH3OH$ which has never been identified.