A low temperature investigation of the gas-phase N(2D) + NO reaction. Towards a viable source of N(2D) atoms for kinetic studies in astrochemistry

Abstract

The gas-phase reaction of metastable atomic nitrogen N(²D) with nitric oxide has been investigated over the 296–50 K temperature range using a supersonic flow reactor. As N(²D) could not be produced photolytically in the present work, these excited state atoms were generated instead through the C(³P) + NO → N(²D) + CO reaction while C(³P) atoms were created in situ by the 266 nm pulsed laser photolysis of CBr₄ precursor molecules. The kinetics of N(²D) atoms were followed on-resonance by vacuum ultraviolet laser induced fluorescence at 116.7 nm. The measured rate constants for the N(²D) + NO reaction are in excellent agreement with most of the earlier work at room temperature and represent the only available kinetic data for this process below 296 K. The rate constants are seen to increase slightly as the temperature falls to 100 K with a more substantial increase at even lower temperature; a finding which is not reproduced by theoretical work. The prospects for using this chemical source of N(²D) atoms in future studies of a wide range of N(²D) atom reactions are discussed.