Time-resolved infrared spectroscopy of ethanol monomers in liquid solution: molecular reorientation and energy relaxation times

Two-color pump-probe spectroscopy has been performed with subpicosecond time resolution in the CH- and OH-stretching regions of ethanol monomers dissolved in carbon tetrachloride in the temperature range from 259 to 333 K. From the isotropic component of the probe transmission signal we deduce the lifetime of the OH-stretching vibration to be T1 = 8 ± 1 ps while the molecular reorientation is directly observed from the anisotropic signal to occur with τor = 2 ± 0.5 ps at room temperature. Additional information on the relaxation pathway of the excited OH-strecthing and on the asymmetric CH3-stretching vibration of ethanol is presented as well as evidence for an inhomogeneous broadening of the monomeric OH-vibration.