An experimental and theoretical investigation of the N + C2 reaction at low temperature

TL;DR

This study combines experimental measurements and quantum dynamics calculations to investigate the N + C2 reaction at low temperatures, revealing its potential significance in astrochemical environments.

Contribution

It provides the first combined experimental and theoretical analysis of the N + C2 reaction at low temperatures, with implications for astrochemistry.

Findings

Rate constants decrease at low temperatures, more rapidly experimentally than theoretically.

The potential energy surface is barrierless with deep wells, indicating efficient reaction pathways.

The reaction may be a major source of CN in dense interstellar clouds.

Abstract

Rate constants for the N + C2 reaction have been measured in a continuous supersonic flow reactor over the range 57 K to 296 K by the relative rate technique employing the N + OH - H + NO reaction as a reference. Excess concentrations of atomic nitrogen were produced by the microwave discharge method and C2 and OH radicals were created by the in-situ pulsed laser photolysis of precursor molecules C2Br4 and H2O2 respectively. In parallel, quantum dynamics calculations were performed based on an accurate global potential energy surfaces for the three lowest lying quartet states of the C2N molecule. The 14A" potential energy surface is barrierless, having two deep potential wells corresponding to the NCC and CNC intermediates. Both the experimental and theoretical work show that the rate constant decreases to low temperature, although the experimentally measured values fall more rapidly than the theoretical ones except at the lowest temperatures. Astrochemical simulations indicate that this reaction could be the dominant source of CN in dense interstellar clouds.