Ultrafast anisotropy decay of coherent excitations and the non-coincidence effect for delocalized vibrational modes in liquids

The relation between the ultrafast anisotropy decay of coherent vibrational excitations and the non-coincidence effect of vibrational bands is examined theoretically. A Stockmayer fluid with a one-dimensional oscillator buried in each particle is used as a model liquid system. It is shown that delocalization of vibrational modes with a set of transition dipole coupling parameters typical of the OH stretching modes gives rise to an ultrafast decay of transient absorption anisotropy and a large magnitude of the non-coincidence effect. The relation with the widths of the vibrational bands due to the transition dipole coupling mechanism is also discussed.