Mechanisms of Radiation-Induced Degradation of CFCl₃ and CF₂Cl₂ in Noble-Gas Matrixes: An Evidence for “Hot” Ionic Channels in the Solid Phase

Abstract

The X-ray-induced transformations of simple chlorofluorocarbons (CFCl and CFCl) in solid noble-gas matrixes (Ne, Ar, Kr, and Xe) at 7 K were studied in order to elucidate basic mechanisms of the radiation-chemical degradation with possible implications for stratospheric and extraterrestrial ice chemistry. The decomposition of parent molecules and formation of products were monitored by FTIR spectroscopy, and the identification was supported by ab initio calculations at the CCSD(T) level. It was shown that the ionic reaction channels were predominating in most cases (except for CFCl/Xe system). The primary radical cations (CFCl and CFCl) are either stabilized in matrixes or undergo fragmentation to yield the corresponding secondary cations (CFCl, CCl, CFCl) and halogen atoms. The probability of fragmentation through different channels demonstrates a remarkable matrix dependence, which was explained by the effect of excess energy resulting from the exothermic positive hole transfer from matrix atoms to freon molecules. A qualitative correlation between "hot" ionic fragmentation at low temperatures and gas-phase ion energetics was found. However, dissociative electron attachment leads to formation of neutral radicals (CFCl or CFCl) and chloride anions. One more possible way of dissociative electron attachment in the case of CFCl is formation of CF and Cl. A general scheme of the radiation-induced processes is proposed.

Atomic basis functions for molecular electronic structure calculations

“…The atomic basis sets are now made available 93 that allow quantitative calculations of the structure and energetics of typical molecular systems. We are somewhat sorry for our belated report, for they have already been, and are being, used by our colleagues in their studies of unusual molecules under the unusual conditions of lowtemperature high-energy chemistry [94][95][96][97][98][99][100] .…”

The Radiation Chemistry of NH3···CO Complex in Cryogenic Media as Studied by Matrix Isolation

“…Taking into account the known IE values for Ar, Kr, and Xe (15.75, 14.0, and 12.1 eV, respectively), one may get estimated ΔIE values of 5.6, 3.9, and 2 eV, for Ar, Kr, and Xe, respectively. This difference may have a strong effect on distribution of the reaction channels (see, e.g., refs , , and ) and is crucially important for explanation of the matrix effects. Such consideration, previously applied to the isolated molecules, is also valid for complexes.…”