Probabilistic representations of partial branching ratios: bridging the gap between experiments and chemical models

Abstract

Dissociative recombination (DR) of polyatomic positive ions with electrons is a very complex process, for which the breakup patterns into neutral fragments are presently unpredictable. Measured branching ratios to the various products channels are thus the only data source for modelers of chemical plasmas. Because of limited detector resolution, data for many ions are incomplete, and implementation of DR processes in chemical models is problematic. In a recent paper [Plessis S et al. 2010 J. Chem. Phys. 133 134110], we proposed a novel approach, based on probabilistic trees, enabling modelers to fully account for the hierarchy of available information. For the first time, we were able to build a chemical model for Titan's ionosphere including all available data about DR branching ratios. The improvement on previous models is considerable, and the data needs for Titan are redefined accordingly.