Vibrational overtone spectroscopy of jet-cooled methanol from 5000 to 14 000 cm-1

Spectra of jet-cooled methanol in the overtone and combination region from 5000 to 14 000 cm^-1 have been obtained by means of infrared laser-assisted photofragment spectroscopy. Many of the observed features are assigned to combination bands of the type nν₁+ν₆, nν₁+ν₈, and nν₁+ν₆+ν₈ (n=1,2,3), where ν₁ is the OH stretch, ν₆ is the OH bend, and ν₈ is the CO stretch. These bands show sharp torsion-rotation structure with features as narrow as 0.1 cm^-1. We also observe CH stretch overtones that are weaker than the OH containing combination bands and lack distinct torsion-rotation structure above v_CH=2. The extent of observed structure on these bands allows us to place limits on the intramolecular vibrational energy redistribution decay rates in the upper vibrational states. We report a global fit of the observed band centers to a simple expression involving low-order anharmonicity constants.