QUANTUM DYNAMICS OF THE WALDEN INVERSION REACTION CL--]CLCH3+CL-(CH3CL)

Quantum scattering calculations on the S(N)2 reaction Cl- + CH3Cl-->Cl CH3+Cl- are reported. The rotating bond approximation (RBA) has been a dapted so that three degrees of freedom including the C-Cl stretching vibration and the CH3 umbrella mode are treated explicitly. The calcul ations have been done with minor modifications of a potential due to V ande Linde and Hase. It is found that initial excitation of the C-Cl v ibration has a large effect on the reaction probabilities, while excit ation of the CH3 umbrella vibration is less significant. The reaction is dominated by scattering resonances with lifetimes ranging from 0.1 to 10 ps. It is found that the length of the C-Cl bond at the transiti on state of the reaction has a particularly pronounced effect on the r eaction probabilities. The magnitude of the quantum reaction probabili ties compares quite well with those calculated using the quasiclassica l trajectory method. (C) 1997 American Institute of Physics.