{
  "abstract": "Context: The methyl cation (CH$_3^+$) was discovered through the detection of a 7 µm (1400 cm-1) band observed in the d203-506 protoplanetary disk in the Orion nebula using the MIRI-MRS spectrometer on board the JWST. This feature has now been reported in numerous astronomical sources. The initial detection was based on simulations of its coinciding and interacting bending modes (ν₂/ν₄) using coarse laboratory and theoretical data, and combined to astronomical data with an absolute wavelength calibration of only several cm -1 . A first spectroscopic assignment of the lines was enabled by later quantum chemical calculations. However, a full spectroscopic assignment of the astronomically observed features in the 7 µm range is awaiting high-resolution laboratory measurements and a more robust wavelength calibration of the MIRI-MRS data. Aims: We present a laboratory high-resolution study of the ν₂/ν₄ bending vibrations of CH$_3^+$ in order to provide accurate and calibrated data for the spectroscopic analysis of JWST detections of this species. Methods: The rovibrational structure of the ν₂/ν₄ bending vibrations of CH$_3^+$ was studied in a cryogenic 22-pole ion trap apparatus at 10 K. For the detection of the vibrational excitation, the efficient leak-out spectroscopy method was used, in combination with a highresolution quantum cascade laser operating at 7 µm. This was combined with MIRI-MRS data of d203-506 reduced with improved wavelength calibration. Results: We were able to measure 49 rovibrational lines of the ν₂/ν₄ band up to J′′ = 6 between 1330 and 1440 cm-1 (6.9-7.5 µm) in high resolution. The measurement accuracy and precision of about 0.001 and 0.0007 cm-1 , respectively, allow spectroscopic constants and line predictions to be derived with high confidence, and thus permit accurate (Doppler velocity) diagnostics of CH$_3^+$ lines with JWST.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": null,
  "author_total": 9,
  "authors": [
    {
      "name": "Thomas Salomon"
    },
    {
      "name": "Ilane Schroetter"
    },
    {
      "name": "Olivier Berné"
    },
    {
      "name": "P. Bryan Changala"
    },
    {
      "name": "Marie-Aline Martin-Drumel"
    },
    {
      "name": "Yoko Okada"
    },
    {
      "name": "Markus Röllig"
    },
    {
      "name": "Stephan Schlemmer"
    },
    {
      "name": "Oskar Asvany"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/a0eb5zpg0h1fc.bib",
  "cited_by": 1,
  "doi": "10.1051/0004-6361/202660397",
  "fulltext_url": null,
  "id": "a0eb5zpg0h1fc",
  "issns": [
    "0004-6361",
    "1432-0746"
  ],
  "landing_url": "https://hal.science/hal-05746653v1",
  "language": "en",
  "licence": "CC-BY-4.0",
  "licence_label": "CC BY 4.0",
  "licence_source": "article",
  "licence_url": "https://creativecommons.org/licenses/by/4.0/",
  "metadata_licence": null,
  "native_subjects": [
    [
      "hal",
      "0.phys"
    ],
    [
      "hal",
      "0.sdu"
    ],
    [
      "hal",
      "1.phys.phys"
    ],
    [
      "hal",
      "1.sdu.astr"
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    [
      "hal",
      "2.phys.phys.phys-chem-ph"
    ],
    [
      "openalex",
      "1607|Spectroscopy and Laser Applications"
    ]
  ],
  "openalex": "W7166093293",
  "pdf_url": "https://hal.science/hal-05746653/document",
  "pmcid": null,
  "pmid": null,
  "published": "2026-09-11",
  "publisher": "EDP Sciences",
  "ris": "https://research.draconitic.com/paper/a0eb5zpg0h1fc.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:17:33Z",
      "native_id": "hal-05746653",
      "source": "hal",
      "url": "https://hal.science/hal-05746653v1"
    }
  ],
  "subjects": [
    {
      "field": "astronomy",
      "origin": "hal:1.sdu.astr",
      "subfield": "general"
    },
    {
      "field": "chemistry",
      "origin": "hal:2.phys.phys.phys-chem-ph",
      "subfield": "physical"
    },
    {
      "field": "earth",
      "origin": "hal:0.sdu",
      "subfield": "general"
    },
    {
      "field": "physics",
      "origin": "hal:0.phys",
      "subfield": "general"
    }
  ],
  "title": "High-resolution laboratory study of the ν₂/ν₄ bending motion of CH$_3^+$ and assignment of its astronomically observed lines",
  "title_text": "High-resolution laboratory study of the ν₂/ν₄ bending motion of CH_3^+ and assignment of its astronomically observed lines",
  "type": "peer-reviewed",
  "updated_at": "2026-10-30T12:17:33Z",
  "url": "https://research.draconitic.com/paper/a0eb5zpg0h1fc",
  "venue": "Astronomy & Astrophysics - A&A",
  "versions": []
}