Reactions of sulfur and oxygen containing anions with nitrogen and oxygen atoms: A comparative study

Abstract

Sulfur‒containing anions are expected to exist in molecular clouds and other astrochemical environments due to the relative abundance of sulfur and the predicted stability of the anions. Furthermore, nitrogen and oxygen atoms are of high abundance in the interstellar medium. Therefore, reactions of nitrogen and oxygen atoms with small sulfur‒containing anions, SCN−, CH3COS−, C6H5COS−, −SCH2COOH, C6H5S−, and related oxygen‒containing anions, OCN−, CH3COO−, C6H5COO−, HOCH2COO−, C6H5O−, have been studied both experimentally and computationally. The experimental results show that none of the studied anions react with nitrogen atoms. All of the studied anions with the exception of OCN− react with oxygen atoms, and the reaction channels are more diverse than those for the previously studied reactions with hydrogen atoms. In addition to the associative electron detachment (AED) channel, some ionic products such as CN−, CH3COO−, C6H5COO−, HO− and S− were observed. A sulfur‒oxygen exchange channel was observed in the reactions of oxygen atoms with CH3COS−, C6H5COS− and C6H5S− anions. A sulfur abstraction channel was observed in the reactions of oxygen atoms with SCN− and −SCH2COOH anions. The rate constants for reactions between sulfur‒containing anions and oxygen atoms are found to be generally higher than for the related oxygen‒containing anions. Density functional theory calculations were conducted to provide insight into the experimental results.