Classical trajectory study of internal energy distributions in unimolecular processes

Abstract

The method of classical trajectories has been used to study the flow of energy in a molecular system (similar to the molecules CD3Cl and CD3H) representing a chemical activation experiment. Energy distributions are obtained both before and after the breakup of the activated molecule by means of a correlation function technique. Four different potential energy surfaces are employed. It is found that the initial distribution of energy in the activated molecule may or may not be random, depending on the details of the particular surface. This distribution becomes random in less than 5×10−12 sec. The distribution of energy in the final product (CD3) is found to be randomly distributed (as predicted by RRKM theory including angular momentum considerations) for a surface with no exit channel barrier or strong intermode couplings. When these special forces are present nonrandom energy distributions result. Product channel barriers result in an excess of translational energy and exit channel intermode couplings result in nonrandom vibrational distributions. Angular momentum considerations are found to be important in matching the predictions of RRKM theory with the calculations.