Conformational dependence of intramolecular vibrational redistribution in methanol

Previous state-selected spectra of methanol in the 5ν1 OH stretch overtone region [O. V. Boyarkin, T. R. Rizzo, and D. S. Perry, J. Chem. Phys. 110 (23), 11346 (1999)] revealed structure indicating intramolecular vibrational redistribution (IVR) on three timescales. Whereas in that work, methanol in the 5ν1 bright state was prepared close to the staggered conformation, methanol in the “partially eclipsed” conformation is prepared here by double resonance excitation through a torsionally excited intermediate state. The excited molecules are detected by infrared laser assisted photofragment spectroscopy (IRLAPS). In partially eclipsed methanol, the strong coupling of the ν1 OH stretch to the ν2 CH stretch becomes weaker, but the coupling responsible for the widths of the narrowest features becomes stronger.