A direct interaction model for chemiluminescent reactions

Abstract

A fully general direct interaction with product repulsion (DIPR) model is developed to aid in the interpretation of product population and alignment data from beam‐gas chemiluminescence reactions of the type: A+BC→AB*+C, where AB* is an electronically excited diatomic product. In this model an electron jump occurs at relatively large A–BC reagent separation which initiates a strong repulsive interaction in BC. This is followed by an attractive interaction between A and B, which is less rapid than the BC repulsion. Product repulsion is taken to be distributed as in photodissociation (the DIP extension of the DIPR model), and the attractive and repulsive energy releases are considered to be separable. The electronic energy of the BC product is subtracted from the total available energy to yield an effective exothermicity which is set equal to the sum of the attractive and repulsive energies. Given reaction exothermicity, reagent and product molecular constants, and repulsive interaction parameters, this model yields the product alignment, vibrational distribution, and rotational distribution for each possible product electronic state. Application to the Ca(¹S₀)+F₂→CaF(B ²∑⁺)+F reaction shows good agreement with experimental results. It is suggested for Ca+F₂ that the CaF* alignment originates from a collinear orientational preference for reaction of the reagents.