BRIDGING THE GAP BETWEEN THE ULTRAFAST AND THE ULTRASLOW

A Brownian simulation of a microscopic pseudo-unimolecular reversible reaction in one-dimension is reported over a huge time range for varyi ng values of the dissociation parameter. The simulation shows how the time behavior of the approach to equilibrium of the binding probabilit y, which is predominantly power-law for ultrafast dissociation, change s to a faster decay law as dissociation slows down. In terms of the me an-field approximations which are compared with the simulations, the u ltrafast dissociation limit is characterized as ''superposition domina ted'' whereas the ulraslow limit is ''convolution dominated''.