On the product electronic state distribution in reactions of alkali dimers with halogen atoms

The distribution of product electronic states from the reactions M₂ + X → MX + M^* for MX = KCl, KBr, and RbBr is re-examined from the information theoretic viewpoint, using a hierarchy of prior distributions. Good agreement with experimental line intensities is achieved using a surprisal linear in the fraction of the total energy in electronic excitation with a small "temperature-like" suprisal parameter (λ_q {less-than or approximate} 0.4 for the most precise of these priors). The continuous rigid rotor harmonic oscillator (RRHO) prior is shown to produce equally good agreement (with λq {less-than or approximate} 1), thus providing a simple analytical expression for branching ratios between product electronic states.