Systematic investigation of CO₂ : NH₃ ice mixtures using mid-IR and VUV spectroscopy – part 1: thermal processing

Abstract

The stoichiometric mixing ratio of CO2 : NH3 ices determines both the initial chemical and physical properties of the ices and their evolution through thermal processing including CO2 bonding environment, NH3 crystallite size and amount of residue.

Systems Astrochemistry: A New Doctrine for Experimental Studies

“…The challenge thus is to learn from such a working paradigm to develop a coherent understanding of the formation of COMs in a structured yet relevant manner. Indeed, the need for a more systematic approach has already been referred to in a number of publications (e.g., Carota et al, 2015;Gentili 2020;James et al, 2020).…”

Mid-IR and VUV spectroscopic characterisation of thermally processed and electron irradiated CO2 astrophysical ice analogues

“…Although perhaps less popular than infrared spectroscopy, electronic spectroscopy has also been used in astrochemical studies of CO2 ice analogues (e.g., Mason et al 2006, Pavithraa et al 2019, James et al 2019, James et al 2020. Between 120 nm (10.3 eV) and 180 nm (6.9 eV), CO2 ice presents two broad absorption bands centred about 125 nm (9.9 eV) and 141 nm (8.8 eV) corresponding to the 1 Πg ← 1 Σg + and the 1 Δu ← 1 Σg + transitions, respectively.…”

“…Indeed, to the best of the authors' knowledge, there is no report currently available where the primary focus is the thermal evolution of the electronic absorption spectra of CO2 ice. The work of James et al (2020) did make mention of such a processing, but was more focused on the thermal processing of mixed CO2:NH3 ices and the resultant chemistry as monitored in the vacuum-ultraviolet. As such, there currently exists a gap in the literature in this regard.…”

Systematic investigation of CO2 : NH3 ice mixtures using mid-IR and VUV spectroscopy – part 2: electron irradiation and thermal processing

“…Interstellar ice analogue experiments play an important role in understanding molecular synthesis in the interstellar medium (ISM), and systematic investigations into the experimental parameters can provide a wealth of information. In James et al , 1 henceforth referred to as RJ20, we demonstrated the impact that one discrete experimental parameter, the stoichiometric mixing ratio, has on both the chemical and physical properties of CO 2 : NH 3 ice mixtures from deposition at 20 K and throughout thermal processing. For example, the NH 3 -rich CO 2 : NH 3 mixtures ( e.g.…”

“…Ammonium carbamate ([NH 4 ][H 2 NCO 2 ]) and carbamic acid (H 2 NCOOH) were reported as UV processing products at 10 K, ammonium carbamate was reported as a product for 9-20 eV electron irradiation at 10 K and carbamic acid as a product for 144 keV S 9+ ion processing at 16 K. We note that ammonium carbamate, or both ammonium carbamate and carbamic acid, were identied as the thermal products in previous non-irradiated studies. 1,3,[5][6][7][8][9][10][11][12] In addition to ammonium carbamate and/or carbamic acid CO, 4,5 OCN À , 4,5 N 2 O (ref. 6) and ammonium formate 5,6 were reported.…”