Vibrational spectroscopy of HOD in liquid D2O.: VII.: Temperature and frequency dependence of the OH stretch lifetime

Recent experiments have shown that the vibrational lifetime of the OH stretch fundamental of dilute HOD in liquid D2O has fascinating dependences on temperature and excitation frequency. In particular, the lifetime increases with increasing temperature and increases with increasing excitation frequency. Using the theoretical model for vibrational relaxation in this system that we developed previously, we calculate the temperature and frequency dependence of the lifetime, reproducing the observed experimental trends. The physical origins of both effects are similar, and involve the dependence of the energy gap between the OH fundamental and the bend overtone (of HOD) on temperature and frequency. The success of our model in describing the experiments provides some support for the relaxation mechanism it implies, which primarily involves direct excitation of the bend overtone. (C) 2003 American Institute of Physics.