The Reaction Between Atomic Carbon And Molecular Nitrogen As A Source Of Cyanamide And Carbodiimide On Interstellar Ices

Reactions occurring on the ice-covered surfaces of interstellar dust grains are considered to be among the most important sources of complex species in the interstellar medium. Despite this, molecules such as cyanamide, NH₂CN, are largely underpredicted by current astrochemical models suggesting that the network of reactions currently used to describe this species and its tautomer carbodiimide, HNCNH, are incomplete.

Here, we performed a theoretical investigation of the reaction of ground state atomic carbon C(3P) with molecular nitrogen N₂ in both the gas-phase and on the surface of amorphous solid water (ASW) clusters to examine its potential importance in the formation of NH₂2CN and HNCNH.

We show that the reaction of gas-phase C-atoms with N₂ molecules already present on the ASW surface results in the barrierless formation of CNN. Following exothermic hydrogenation reactions, the N-N bond of the C-N-N bearing intermediates is broken allowing the formation of molecules with N-C-N backbones through cyclic intermediates over low barriers.

To test the importance of these processes to NH₂CN and HNCNH formation, these reactions were included in a three-phase astrochemical model of low-mass protostellar evolution employing a reaction network that was updated to better describe the formation and destruction pathways of related small nitrogen bearing molecules.

These simulations demonstrate that the ice surface reaction between C and N2 represents by far the dominant source of NH₂CN and HNCNH in protostellar environments and in dense clouds.

Kevin M. Hickson, Jean-Christophe Loison, Audrey Coutens

Comments: Published in ACS Earth and Space Chemistry
Subjects: Astrophysics of Galaxies (astro-ph.GA)
Cite as: arXiv:2604.15930 [astro-ph.GA] (or arXiv:2604.15930v1 [astro-ph.GA] for this version)
https://doi.org/10.48550/arXiv.2604.15930
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Related DOI:
https://doi.org/10.1021/acsearthspacechem.6c00032
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Submission history
From: Kevin Hickson
[v1] Fri, 17 Apr 2026 10:43:15 UTC (1,384 KB)
https://arxiv.org/abs/2604.15930

Astrobiology, Astrochemistry,