DIRECT FEMTOSECOND MEASUREMENTS OF SINGLE COLLISION DOMINATED GEMINATE RECOMBINATION TIMES OF SMALL MOLECULES IN LIQUIDS

We report the femtosecond transient absorption spectra of the CH2I2 photoproduct of the methylene iodide (CH2I2) photodissociation. The results indicate a disappearance of this photofragment on a almost-equal-to 350 fs time scale in several different solvents. The implication is that in these simple liquids, methylene iodide is undergoing geminate recombination. Recombination yields, but not rates are shown to be solvent dependent. Comparison to the photodissociation dynamics of other small molecules suggests that the kinetics of geminate recombination are dominated by a single collision with the surrounding solvent cage in a large class of molecules and that the process may be universal.