Reactions of oxygen atoms with fluoroform and its radiolysis products: matrix isolation and ab initio study

Abstract

The investigation of the reactions of oxygen atoms with fluoroform (CHF₃) molecules and products of their degradation present significant interest for better understanding of the impact of chemically inert fluorinated compounds on atmospheric chemistry and may provide a deeper insight into mechanisms of chemical processes occurring under the action of hard UV and ionizing radiation. In the present study we applied a matrix isolation technique with FTIR spectroscopic detection combined with ab initio calculations to address this issue. It was found that the reactions of “hot” (translationally excited) O(¹D) atoms produced by X-ray or UV radiation from appropriate precursors (N₂O or H₂O) resulted in the formation of carbonyl fluoride (COF₂) and its complex with HF. The complex was detected and characterized for the first time. Singlet oxygen atoms also probably react with the products of radiation-induced degradation of fluoroform (CF₃ and CF₂). Additionally, the reaction of “hot” O(³P) atoms with fluoroform may occur to a certain extent yielding the CF₃ radical. No evidence for the reactions of thermal O(³P) atoms with CHF₃ or products of its degradation was found under the experimental conditions used. The implications of the results of this model study for understanding the evolution of fluoroform in the upper layers of the stratosphere and ionosphere are discussed.