Knowledge Bank

Overtone spectra of jet-cooled methanol have been recorded from 5,000 to $14,000cm-1$ using Infrared Laser Assisted Photofragment Spectroscopy (IRLAPS) for the detection of the vibrationally excited molecules. In addition to the OH stretch overtones $(n\nu 1)$, the major components of the spectra are the overtones of the CH stretch (up to $5\nu CH$) as well as combinations of the OH stretch with the CO stretch $(n\nu 1+\nu 8)$, the COH bend $(n\nu 1+\nu 6)$, and both $(n\nu 1+\nu 6+\nu 8)$. These data, together with photoacoustic data [1] up to $18,250cm-1$ and previously reported IRLAPS data [2] up to $22,166cm-1$ have been fit to an anharmonic Hamiltonian. In this Hamiltonian, the CH stretch vibrations are treated as a pair of local modes, $va$ and $v6$ for $vCH=3$ and higher. The other modes are treated as the usual normal vibrations.