{
  "abstract": "Gas--grain astrochemical models predict that a substantial fraction of elemental nitrogen in dense cores and protoplanetary disks is locked in molecular nitrogen (N$_2$), in the gas or ice phase, although interstellar N$_2$ ice has not been directly identified. Rosetta measurements at comet 67P/Churyumov--Gerasimenko showed strong N$_2$ depletion relative to CO, while NH$_3$ was the dominant detected nitrogen-bearing ice. We experimentally quantify the conversion of NH$_3$ ice into N$_2$ and N$_2$H$_4$ under astronomically relevant conditions by studying its temperature- and fluence-dependent VUV photochemistry. Experiments were performed under ultra-high vacuum using 40-monolayer NH$_3$ ice at 15, 25, and 70 K irradiated at 115--170 nm to a total fluence of $3.8\\times10^{18}$ photons cm$^{-2}$. Laser desorption with post-ionization reflection time-of-flight mass spectrometry (ReTOF-MS) was used to monitor N$_2$ and N$_2$H$_4$ simultaneously. VUV photolysis efficiently forms both products, with formation kinetics and product ratios depending on temperature and photon fluence. Initial-growth fits gave the highest apparent ice-retained N$_2$ formation yield at 15 K, approximately an order of magnitude above those at 25 and 70 K. The N$_2$/NH$_3$ column-density ratio was determined as a function of fluence and compared with astronomical constraints. These results suggest that NH$_3$ ice photochemistry may provide an additional pathway to N$_2$ ice in cold outer planetary environments.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": "Journal reference: A&A, 712, A235 (2026)",
  "arxiv": "2609.17878",
  "author_total": 6,
  "authors": [
    {
      "name": "P. Samarth"
    },
    {
      "name": "G. Fedoseev"
    },
    {
      "name": "S. Ioppolo"
    },
    {
      "name": "L. Hornekær"
    },
    {
      "name": "E. F. van Dishoeck"
    },
    {
      "name": "K. -J. Chuang"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/9hrr9qxgd2bpn.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2609.17878",
  "fulltext_url": null,
  "id": "9hrr9qxgd2bpn",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2609.17878",
  "language": null,
  "licence": "CC-BY-4.0",
  "licence_label": "CC BY 4.0",
  "licence_source": "article",
  "licence_url": "http://creativecommons.org/licenses/by/4.0/",
  "metadata_licence": "CC0-1.0",
  "native_subjects": [
    [
      "arxiv",
      "astro-ph.EP"
    ],
    [
      "arxiv",
      "astro-ph.GA"
    ],
    [
      "arxiv",
      "astro-ph.IM"
    ]
  ],
  "openalex": null,
  "pdf_url": "https://arxiv.org/pdf/2609.17878",
  "pmcid": null,
  "pmid": null,
  "published": "2026-09-15",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/9hrr9qxgd2bpn.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:22:01Z",
      "native_id": "2609.17878",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2609.17878"
    }
  ],
  "subjects": [
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.GA",
      "subfield": "galaxies"
    },
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.IM",
      "subfield": "instrumentation-methods"
    },
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.EP",
      "subfield": "planetary"
    }
  ],
  "title": "Quantifying the temperature-dependent yields of N$_2$ and N$_2$H$_4$ formation in vacuum-ultraviolet-irradiated NH$_3$ ice",
  "title_text": "Quantifying the temperature-dependent yields of N_2 and N_2H_4 formation in vacuum-ultraviolet-irradiated NH_3 ice",
  "type": "preprint",
  "updated_at": "2026-10-30T12:22:01Z",
  "url": "https://research.draconitic.com/paper/9hrr9qxgd2bpn",
  "venue": "arXiv",
  "versions": [
    {
      "doi": "10.1051/0004-6361/202658992",
      "pid": null,
      "relation": "published-as",
      "title": null,
      "venue": null
    }
  ]
}