FEMTOSECOND LASER SPECTROSCOPY AND COMPUTER-SIMULATIONS OF BARRIERLESS ISOMERIZATION IN SOLUTION

The barrierless isomerization of 1,1-diethyl-4,4-cyanine in alcohol so lutions has been studied with 75-fs laser pulses in transient absorpti on experiments. The measured dynamics are compared with Monte-Carlo si mulations based on the BFO-theory (Bagchi, B.; Fleming, G.R.; Oxtoby, D.W. J. Chem. Phys. 1983.78: 7375) for condensed-phase barrierless iso merizations, and the viscosity dependence of the long-time exponential decay is well reproduced with a coherent set of parameters. In the mo st viscous solvents, early-time (less than or similar to 1 ps) kinetic s are observed which are characteristic of damped wavepacket dynamics in the reaction coordinate.