New Dissociative Recombination Product Branching Fractions and Their Effect on Calculated Interstellar Molecular Abundances

Abstract

Recent storage ring measurements of the complete product distributions for the dissociative recombination of assorted polyatomic ions (H + 3, H 2 O +, H 3 O +, CH + 3) show that there is significantly more fragmentation than previously believed. Generalizing these results, we consider the effect on gas-phase chemical models of dense interstellar clouds when a greater degree of fragmentation is assumed for the products of dissociative recombination reactions. In general, we find salient model results to be surprisingly insensitive to the change. We also generalize some conflicting experimental results for the branching fractions of H 3 O + + e obtained in a flowing afterglow experiment. With this set of generalized branching fractions in our chemical model, there is a stronger change from previous results, especially for more saturated molecules, which are now difficult to produce in the gas phase.