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| Main Authors: | , , , |
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| Format: | Preprint |
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2026
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| Online Access: | https://arxiv.org/abs/2604.17536 |
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| _version_ | 1866913061542035456 |
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| author | Dastider, Saptarshi G. Negi, Amit Singh Mondal, Krishnakanta Cyriac, Jobin |
| author_facet | Dastider, Saptarshi G. Negi, Amit Singh Mondal, Krishnakanta Cyriac, Jobin |
| contents | The recent detections of thioformyl cyanide (HCSCN) and propynethial (HCSCCH) in TMC-1 provide critical insights into the interstellar sulfur inventory, yet their sequestration and survivability on dust grain mantles remain poorly constrained. Here, we present a computational study of the site-specific adsorption of HCSCN and HCSCCH on amorphous solid water (ASW), modelled via water clusters (H2O)n, n = 6-16, at the wB97X-D/def2-TZVP level of theory, corroborated by QTAIM topological analyses and TD-DFT vertical excitations. Our results reveal a highly heterogeneous binding environment, with desorption energies spanning 1500 to 4900 K. Strongly bound cavity sites induce significant Stark shifts in the C=S stretching modes. Crucially, while the ice matrix exerts a negligible solvatochromic shift on UV transition wavelengths, deeply bound CN-cavity configurations exhibit a pronounced hyperchromic enhancement of the oscillator strength. Implementing these site-specific parameters into the UCLCHEM gas-grain code demonstrates that these species undergo a gradual thermal desorption profile rather than a singular sublimation event. Furthermore, the hyperchromic effect establishes a Survival Paradox: while deeply trapped populations are thermodynamically shielded against thermal desorption, they simultaneously possess enhanced UV absorption cross-sections, rendering them vulnerable to photodissociation by the interstellar radiation field prior to sublimation. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2604_17536 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Ice as a Photochemical Shield: Adsorption Energetics and Spectroscopic Modulation of Interstellar Thiocyanates HCSCN and HCSCCH in TMC-1 Dastider, Saptarshi G. Negi, Amit Singh Mondal, Krishnakanta Cyriac, Jobin Astrophysics of Galaxies Chemical Physics Computational Physics The recent detections of thioformyl cyanide (HCSCN) and propynethial (HCSCCH) in TMC-1 provide critical insights into the interstellar sulfur inventory, yet their sequestration and survivability on dust grain mantles remain poorly constrained. Here, we present a computational study of the site-specific adsorption of HCSCN and HCSCCH on amorphous solid water (ASW), modelled via water clusters (H2O)n, n = 6-16, at the wB97X-D/def2-TZVP level of theory, corroborated by QTAIM topological analyses and TD-DFT vertical excitations. Our results reveal a highly heterogeneous binding environment, with desorption energies spanning 1500 to 4900 K. Strongly bound cavity sites induce significant Stark shifts in the C=S stretching modes. Crucially, while the ice matrix exerts a negligible solvatochromic shift on UV transition wavelengths, deeply bound CN-cavity configurations exhibit a pronounced hyperchromic enhancement of the oscillator strength. Implementing these site-specific parameters into the UCLCHEM gas-grain code demonstrates that these species undergo a gradual thermal desorption profile rather than a singular sublimation event. Furthermore, the hyperchromic effect establishes a Survival Paradox: while deeply trapped populations are thermodynamically shielded against thermal desorption, they simultaneously possess enhanced UV absorption cross-sections, rendering them vulnerable to photodissociation by the interstellar radiation field prior to sublimation. |
| title | Ice as a Photochemical Shield: Adsorption Energetics and Spectroscopic Modulation of Interstellar Thiocyanates HCSCN and HCSCCH in TMC-1 |
| topic | Astrophysics of Galaxies Chemical Physics Computational Physics |
| url | https://arxiv.org/abs/2604.17536 |