Vibrationally Excited Products of Bimolecular Exchange Reactions

Abstract

MANY observations of gaseous bimolecular exchange reactions in which vibrationally excited products appear have been interpreted^1–3 in terms of a simple model developed by F. T. Smith². Smith's treatment, based on the kinematics of a collinear collision, predicts that the upper limit to the fraction of energy of reaction which may appear as product vibration is sin² β, where β is the angle between the skewed axes of the potential energy surface on which a sliding mass point represents the progress of the collision. Observed vibrational energies in excess of the amount calculated in this way have usually been interpreted as contravening Smith's model. It is the purpose of the present communication to point out that when the Smith treatment is generalized by lifting the restriction that collisions be collinear, it becomes apparent that the fraction being calculated is more nearly a lower limit than an upper. As a result certain changes in the interpretation of the experimental evidence are required.