There is now a four order of magnitude time range (≈100 fs to 1 ns) over which molecular dynamic calculations can overlap short light pulse experimental measurements to probe the microscopic nature of chemical processes. In this paper we combine theoretical molecular dynamics calculations of picosecond transient spectra with experimental measurements of such spectra to probe the molecular dynamics of a chemical reaction in solution. The example illustrated is the photodissociation of Ι2 followed by solvent caging, radical recombination to form a new highly vibra-tionally excited Ι2 molecule, and the subsequent decay of this vibrational energy to the solvent. We suggest, as Nes-bitt and Hynes do also, that the lifetimes observed in Ι2 picosecond absorption experiments may not be due to gem-inate recombination times, but perhaps to the time necessary for the recombined Ι2 molecules to vibrationally decay to levels with high Franck-Condon factors for absorption.
Peter H. Berens,
Kent R. Wilson,
"Picosecond Dynamics Of Solution Reactions", Proc. SPIE 0322, Picosecond Lasers and Applications, (23 April 1982); doi: 10.1117/12.933244; https://doi.org/10.1117/12.933244