Solvent dynamics: Modified Rice–Ramsperger–Kassel–Marcus theory. II. Vibrationally assisted case

Expressions are given for a solvent dynamics-modified Rice–Ramsperger–Kassel–Marcus ~RRKM! theory for clusters. The role of vibrational assistance across the transition state region is included. The usual differential equation for motion along the slow coordinate X in constant temperature systems is modified so as to apply to microcanonical systems. A negative entropy term, 2Sv(X), replaces the (1/T)]U/]X or (1/T)]G/]X which appears in canonical systems. Expressions are obtained for the RRKM-type rate constant k(X) and for the Sv(X) which appear in the differential equation. An approximate solution for steady-state conditions is given for the case that the ‘‘reaction window’’ is narrow. The solution then takes on a simple functional form. The validity of the assumption can be checked a posteriori. Recrossings of the transition state are included and the condition under which the treatment approaches that in Part I is described. © 1996 American Institute of Physics. @S0021-9606~96!51137-2#