The C(3P) + NH3 reaction in interstellar chemistry: I. Investigation of the product formation channels

TL;DR

This study investigates the reaction pathways of ground state carbon atoms with ammonia, revealing that hydrogen and H2CN are the primary products, supported by experiments and electronic structure calculations relevant to interstellar chemistry.

Contribution

It combines experimental and theoretical methods to identify reaction products and mechanisms of C(3P) with NH3 at low temperatures, advancing understanding of interstellar chemical processes.

Findings

H + H2CN is the dominant product channel.

Reaction occurs efficiently at low temperatures (50-330 K).

Electronic structure calculations support experimental results.

Abstract

The product formation channels of ground state carbon atoms, C(3P), reacting with ammonia, NH3, have been investigated using two complementary experiments and electronic structure calculations. Reaction products are detected in a gas flow tube experiment (330 K, 4 Torr) using tunable VUV photoionization coupled with time of flight mass spectrometry. Temporal profiles of the species formed and photoionization spectra are used to identify primary products of the C + NH3 reaction. In addition, H-atom formation is monitored by VUV laser induced fluorescence from room temperature to 50 K in a supersonic gas flow generated by the Laval nozzle technique. Electronic structure calculations are performed to derive intermediates, transition states and complexes formed along the reaction coordinate. The combination of photoionization and laser induced fluorescence experiments supported by theoretical calculations indicate that in the temperature and pressure range investigated, the H + H2CN production channel represents 100% of the product yield for this reaction. Kinetics measurements of the title reaction down to 50 K and the effect of the new rate constants on interstellar nitrogen hydride abundances using a model of dense interstellar clouds are reported in paper II.