The Reaction between Atomic Carbon and Molecular Nitrogen as a Source of Cyanamide and Carbodiimide on Interstellar Ices

Abstract

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 NH2CN 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.

Published in ACS Earth and Space Chemistry

References in corpus (36)

• The ALMA Protostellar Interferometric Line Survey (PILS): First results from an unbiased submillimeter wavelength line survey of the Class 0 protostellar binary IRAS 16293-2422 with ALMA
• Gas and grain chemical composition in cold cores as predicted by the Nautilus 3-phase model
• Binding energies: new values and impact on the efficiency of chemical desorption
• Oxygen depletion in dense molecular clouds: a clue to a low O2 abundance?
• The ALMA-PILS survey: First detections of deuterated formamide and deuterated isocyanic acid in the interstellar medium
• Can Formamide Be Formed on Interstellar Ice? An Atomistic Perspective
• Binding energies of interstellar molecules on crystalline and amorphous models of water ice by ab-initio calculations
• Nitrogen chemistry and depletion in starless cores
• Nitrogen isotopic ratios in Barnard 1: a consistent study of the N2H+, NH3, CN, HCN and HNC isotopologues
• Elemental nitrogen partitioning in dense interstellar clouds
• Reactivity of HCO with CH3 and NH2 on Water Ice Surfaces. A Comprehensive Accurate Quantum Chemistry Study
• An Approach to Estimate the Binding energy of Interstellar Species
• Adsorption energies of carbon, nitrogen, and oxygen atoms on the low-temperature amorphous water ice: A systematic estimation from quantum chemistry calculations
• Efficiency of non-thermal desorptions in cold-core conditions. Testing the sputtering of grain mantles induced by cosmic rays
• Nitrogen Isotopic Fractionation in Interstellar Ammonia
• First detection of cyanamide (NH${}_2$CN) towards solar-type protostars
• Interstellar Carbodiimide (HNCNH) - A New Astronomical Detection from the GBT PRIMOS Survey via Maser Emission Features
• The ALMA-PILS survey: First detection of the unsaturated 3-carbon molecules Propenal (C${}_2$H${}_3$CHO) and Propylene (C${}_3$H${}_6$) towards IRAS 16293$-$2422 B
• Deuteration of ammonia with D atoms on oxidized partly ASW covered graphite surface
• Thermal desorption of formamide and methylamine from graphite and amorphous water ice surfaces
• Chemical and physical characterization of collapsing low-mass prestellar dense cores
• Carbon Atom Reactivity with Amorphous Solid Water: H${}_2$O Catalyzed Formation of H${}_2$CO
• ${}^{14}$N/${}^{15}$N ratio measurements in prestellar cores with N${}_2$H${}^{+}$: new evidence of ${}^{15}$N-antifractionation
• Depletion of heavy nitrogen in the cold gas of star-forming regions
• Hydrogenation of accreting C-atoms and CO molecules -- simulating ketene and acetaldehyde formation under dark and translucent cloud conditions
• Chemical nitrogen fractionation in dense molecular clouds
• Low temperature rate constants for the N(4S) + CH(X2Πr) reaction. Implications for N2 formation cycles in dense interstellar clouds
• The ALMA-PILS survey: First tentative detection of 3-hydroxypropenal (HOCHCHCHO) in the interstellar medium and chemical modeling of the C${}_3$H${}_4$O${}_2$ isomers
• Formation of complex organic molecules on interstellar CO ices? Insights from computational chemistry simulations
• Surface Diffusion of Carbon Atoms as a Driver of Interstellar Organic Chemistry
• First measurement of the 14N/15N ratio in the analogue of the Sun progenitor OMC-2 FIR4
• Influence of galactic arm scale dynamics on the molecular composition of the cold and dense ISM II. Molecular oxygen abundance
• Sensitivity Analysis of Aromatic Chemistry to Gas-Phase Kinetics in a Dark Molecular Cloud Model
• Ion-molecule routes towards cycles in TMC-1. An automated study of the C2H4 + CH2CCH+ reaction
• Laboratory spectroscopic study of the ${}^{15}$N isotopomers of cyanamide, H${}_2$NCN, and a search for them toward IRAS 16293$-$2422 B
• A Low Temperature Kinetic Study of the C(3P) + CH3OCH3 Reaction. Rate constants, H-atom Product Yields and Astrochemical Implications