Journal of Physical Chemistry A, Vol.107, No.19, 3606-3611, 2003
Femtosecond photolysis of HOCl(aq): Dissipation of fragment kinetic energy
In this work, we present an experimental study of the energy dependence of the photolysis of aqueous HOCl and the subsequent recombination of the OH and Cl photofragments. Using femtosecond transient absorption spectroscopy, we follow the time-dependent concentration of the fragments. The excess energy in the photolysis is given to the fragments as kinetic energy, and tuning the wavelength enables a study of the energy-dependent thermalization and geminate recombination of the fragments in the liquid environment. The recombination yield and rate are governed by the initial fragment separation, and we deduce an approximately linear dependence of the fragment separation versus the kinetic energy with a slope of 0.13 nm/eV. Performing a simple MD simulation of the system gives qualitative agreement with the observations, although the calculated slope is only 0.04 nm/eV.