Photodissociation dynamics of dihalomethanes in solution studied by ultrafast pump-probe spectroscopy

Summary form only given. Much effort has been put into understanding the photodissociation dynamics of dihalomethanes in the gas phase. In solution, the task is even more challenging since supplementary processes can be present in the condensed phase; one such example is geminate recombination within the cage of solvent molecules. We present observations of the isomers for dihalomethanes, with particular focus on chloroiodomethane (CH/sub 2/ICl). The photodissociation of CH/sub 2/ICI dissolved in acetonitrile was initiated using a femtosecond pulse at 266 nm and the transient absorption was measured out to delays of 300 ps over a spectral region from 330 to 850 nm. The photodissociation leads to formation and subsequent vibrational cooling of a product species, which we suggest is the isomer of chloroiodomethane, CH/sub 2/Cl-I, likely produced via in-cage recombination between the nascent fragments CH/sub 2/Cl and I.