Theoretical Study of the Dissociative Recombination and Vibrational (De-)Excitation of HCNH<sup>+</sup> and Its Isomers by Electron Impact
Protonated hydrogen cyanide, HCNH<sup>+</sup>, is one of the most important molecules of interest in the astrophysical and astrochemical fields. This molecule not only plays the role of a reaction intermediary in various types of interstellar reactions but was also identified in Titan’s...
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| Main Authors: | , |
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| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2024-12-01
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| Series: | Atoms |
| Subjects: | |
| Online Access: | https://www.mdpi.com/2218-2004/12/12/64 |
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| Summary: | Protonated hydrogen cyanide, HCNH<sup>+</sup>, is one of the most important molecules of interest in the astrophysical and astrochemical fields. This molecule not only plays the role of a reaction intermediary in various types of interstellar reactions but was also identified in Titan’s upper atmosphere. The cross sections for the dissociative recombination (DR) and vibrational (de-)excitation (VE and VDE) of HCNH<sup>+</sup> and its <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msubsup><mi>CNH</mi><mn>2</mn><mo>+</mo></msubsup></semantics></math></inline-formula> isomer are computed using a theoretical approach based on a combination of the normal mode approximation for the vibrational states of the target ions and the UK R-matrix code to evaluate electron-ion scattering matrices for fixed geometries of ions. The theoretical convoluted DR cross section for HCNH<sup>+</sup> agrees well with the experimental data and a previous study. It was also found that the DR of the <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msubsup><mi>CNH</mi><mn>2</mn><mo>+</mo></msubsup></semantics></math></inline-formula> isomer is important, which suggests that this ion might be present in DR experiments of HCNH<sup>+</sup>. Moreover, the ab initio calculations performed on the H<sub>2</sub>CN<sup>+</sup> isomer predict that this ion is a transition state. This result was confirmed by the study of the reaction path of the HCNH<sup>+</sup> isomerization that was carried out by evaluating the intrinsic reaction coordinate (IRC). Finally, thermally averaged rate coefficients derived from the cross sections are provided for temperatures in the 10–10,000 K range. A comprehensive set of calculations is performed to assess the uncertainty of the obtained data. These results should help in modeling non-LTE spectra of HCNH<sup>+</sup>, taking into account the role of its most stable isomer, in various astrophysical environments. |
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| ISSN: | 2218-2004 |