Picosecond dynamics of barrier crossing in solution: A study of the conformational change of excited state 1,1′-binaphthyl

Abstract

The rates of optically induced conformational changes of excited state 1,1′-binaphthyl in a series of alcohol solvents were measured by a picosecond laser technique. Excellent agreement with experiment is found for the Kramers model for both the intermediate and high friction regimes using a frequency independent friction coefficient evaluated from classical hydrodynamics. This is the first observation of Kramers behavior in the intermediate friction regime and indicates that deviations from Kramers behavior is not a universal phenomenon in the conformational dynamics of flexible molecules in solution. It also emphasizes the possibility that the observed deviations from the Kramers model can be due to effects other than non-Markovian friction.