Infrared Spectra and Vapor Pressures of Crystalline C₂N₂, with Comparisons to Crystalline HCN

Abstract

In a continuation of our work on nitriles, we have examined cyanogen (C2N2) as a crystalline solid, comparing the results to our recent work on crystalline hydrogen cyanide (HCN). A density and refractive index for C2N2 ice were measured and used to prepare solid samples from which infrared (IR) spectra, band strengths, and optical constants were measured. The vapor pressures (sublimation pressures) of both C2N2 and HCN ices were determined with a quartz-crystal microbalance at temperatures relevant to Titan's atmosphere and much lower than those in the literature. Comparisons of the newly measured low-temperature vapor pressures to values extrapolated from higher temperatures revealed differences on the order of 45 and 130%. The enthalpies of sublimation of C2N2 and HCN in the 120 K region were measured and found to be similar to those at higher temperatures. Comparisons were made to previous spectroscopic work, but hindered in the case of IR intensities by the lack of published details.

Ab Initio Study of the Graphyne-like γ-SiC Nanoflake for Toxic Gas-Sensing Applications

“…The VFs of γ-SiC slightly varied, whereas the VFs of gas molecules suffered a significant variation due to deformation through adsorption (Table ). The values in the parentheses represent the VFs of isolated gas molecules, which satisfies previous reports. − The decrease in stretching VFs of the gas molecules represents an increase in bond lengths and vice versa, which verifies the data listed in Table . No imaginary VFs are observed in the complex systems, which suggests that all of the adsorbed geometries have stable configurations, i.e., the adsorption of the selected gases on the selected sites is dynamically possible.…”

Organic Chemistry in the H2-bearing, CO-rich Interstellar Ice Layer at Temperatures Relevant to Dense Cloud Interiors

“…In addition, Figure 3 shows the TPD curves of three products whose formation could only be confirmed by the QMS during thermal desorption of the irradiated ice samples: C 2 15 N 2 , C 2 H 2 O, and H 15 NCO. IR features corresponding to C 2 H 2 O and H 15 NCO could not be unambiguously detected as their position overlapped with the CO and carbon chain oxide IR bands, respectively (van Broekhuizen et al 2004;Hudson & Ferrante 2020); while the expected C 2 15 N 2 IR integrated absorbance was below our detection limit (Hudson & Gerakines 2023). Formation of C 2 H 2 O was detected in Experiments 1-3 but, like H 2 CO, it significantly decreased in the ice irradiated at 10.0 K. Formation of H 15 NCO was only detected in the samples irradiated at 4.7 and 8.0 K, while formation of C 2 15 N 2 was only observed in the ice irradiated at 10.0 K. We note that the assignment of all identified products was confirmed in Martín-Doménech et al (2020) after energetic processing of isotopically labeled CO:N 2 :H 2 ice samples.…”