Information content of detailed differential reaction cross sections (molecular beam scattering velocity-angle maps) vs resolved product state distributions

Abstract

Information theory provides a quantitative measure of the information content, or entropy deficiency, of different classes of experiments (and computer simulations), e.g., molecular beam scattering and infrared chemiluminescence. Using histogrammic representations of beam‐ or computationally derived polar (velocity‐angle) flux contour maps, the entropy deficiency associated with the product translational recoil and angular distribution is readily calculated. This is compared with that from resolved distributions of product vibrational and rotational states (e.g., from ir chemiluminescence experiments). It appears that the gain in information associated with the knowledge of products’ angular distribution (even with the additional ’’mutual information’’ from the angle–recoil velocity correlation) is often outweighed by the substantial loss of information on the separate vibrational and rotational distributions. This so‐called ’’equivocation’’ or VR→T loss can be an appreciable fraction of the total information content of the product state distribution. Product state angular distributions as obtained recently by the laser‐induced fluorescence technique can provide substantially more information content.