Dynamics of liquid state chemical reactions: Photolysis of molecular iodine in liquid xenon

Abstract

The photodissociation and geminate recombination dynamics of molecular iodine present at infinite dilution in liquid xenon are studied via MTGLE classical stochastic trajectory simulations. The experimentally measured transient picosecond electronic absorption spectrum and geminate quantum yields are computed from the trajectories. The excitation pulse wavelength dependence of the photodynamics is studied. From the wavelength dependence of the dissociation pathway, it is inferred that there are observable consequences of curve-crossing phenomena which manifest themselves in the short-time behavior of the I2 transient electronic absorption spectrum. Also because of the presence of slow vibrational relaxation of the recombining iodine atoms, the apparent asymptote of the transient spectra may not accurately reflect the geminate quantum yield. The probe pulse wavelength dependence of the transient absorption spectrum is also studied. Here it is observed that: (i) Longer wavelength interrogation light yields shorter time scale dynamical information concerning the energy relaxation of nascent I2 molecules. (ii) Interrogation at several probe wavelengths can yield fairly detailed information about the X state time-dependent vibrational level distribution of nascent I2 molecules.