IR spectroscopy of hydrogen-bonded methanol: Vibrational and structural relaxation on the femtosecond time scale

Two-color pump-probe spectroscopy is performed with femtosecond time resolu tion in the OH-stretching region of methanol oligomers in a CCl4 mixture at room temperature. The measured isotropic component of the probe transmissi on signal gives direct access to the lifetime of the OH-stretching vibratio n. It varies between 0.45 and 0.6 ps, increasing with excitation frequency from 3280 to 3400 cm(-1). After vibrational excitation of the OH-mode, fast spectral relaxation and/or vibrational energy migration with subsequent br eaking of the excited oligomers is noticed. Recombination proceeds with a t ime constant of 9 ps, Comparison to earlier work on water and related alcoh ols is also made.