Energy relaxation and reorientation of the OH mode of simple alcohol molecules in different solvents monitored by transient IR spectroscopy

Two-color pump–probe spectroscopy is performed within the OH stretching region of monomeric methanol, 1-decanol, and 2,2-dimethyl-3-ethyl-3-pentanol dissolved in different solvents CnClm. From the isotropic component of the probe transmission signal we deduce the lifetime of the OH stretching vibration to vary between 8 and 10 ps. The molecular reorientation is directly observed from the anisotropic signal to occur in the range of 2 up to 7 ps. Additional information is presented, giving evidence for an inhomogeneous broadening of the monomeric OH vibration and finite phase relaxation of the order of 1 ps.