Picosecond kinetic study of the photoinduced homolysis and heterolysis of diphenylmethyl bromide .2. Role of polarization caging in contact ion pair recombination

Picosecond absorption spectroscopy is used to study the dynamics of the collapse of the diphenylmethyl bromide contact ion pair to form the carbon-bromine bond. The dynamics of the diphenylmethyl cation-bromide anion are probed as a function of temperature. The Arrhenius parameters for the collapse of the contact ion pair to form the carbon-bromine bond are A = 4.9 x 10(11) s(-1) and E(a) = 3.0 kcal/mol. Deviations from equilibrium solvation transition state theory are found, and it is concluded that the collapse of the ion pair occurs in the polarization caging regime.