{
  "abstract": "The low-temperature orientational heat capacity of an interacting multipole pair is conventionally taken to be two-valued: 3/2 k B for axially symmetric moments and 2 k B otherwise. Here I evaluate it for all 101,666,280 molecular geometries of the OMol25 dataset and show that this is the bottom rung of a staircase: the exponent is a count, not a case split, γ = C v / k B = Σ i 1/ p i , which for two rigid nonlinear molecules is exactly γ = D / 2 and leaves only the rungs 3/2, 2 and 5/2. Of 11,325,000 pairs drawn uniformly from the whole dataset none occupies the 3/2 rung ( P < 3.26 x 10 -7 ; structural bound 4.187 x 10 -7 ), and the rest split 12.05% and 87.95% between γ = 2 and 5/2, so nearly the whole molecular world shares one coefficient: 5/2 k B = 20.79 J mol -1 K -1 per mole of pairs. The 3/2 rung is deleted rather than thermally suppressed (a 0.129 Å C-H bending amplitude exceeds the 0.1 Å scale at which a C 3v rotor saturates its axiality defect), so no temperature recovers it.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": null,
  "author_total": 1,
  "authors": [
    {
      "name": "Fuxing Lin",
      "orcid": "0009-0003-7588-6942"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/aazw2cvzh5wkf.bib",
  "cited_by": 0,
  "doi": "10.26434/chemrxiv.15010225/v1",
  "fulltext_url": null,
  "id": "aazw2cvzh5wkf",
  "issns": [],
  "landing_url": "https://chemrxiv.org/doi/full/10.26434/chemrxiv.15010225/v1",
  "language": null,
  "licence": "CC-BY-NC-ND",
  "licence_label": "CC BY-NC-ND",
  "licence_source": "journal",
  "licence_url": "https://creativecommons.org/licenses/by-nc-nd/4.0/",
  "metadata_licence": null,
  "native_subjects": [
    [
      "openalex",
      "1606|Advanced Physical and Chemical Molecular Interactions"
    ]
  ],
  "openalex": "W7221526211",
  "pdf_url": "https://chemrxiv.org/doi/pdf/10.26434/chemrxiv.15010225/v1",
  "pmcid": null,
  "pmid": null,
  "published": "2026-10-11",
  "publisher": "American Chemical Society (ACS)",
  "ris": "https://research.draconitic.com/paper/aazw2cvzh5wkf.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:17:22Z",
      "native_id": "10.26434/chemrxiv.15010225",
      "source": "chemrxiv",
      "url": "https://chemrxiv.org/doi/full/10.26434/chemrxiv.15010225/v2"
    }
  ],
  "subjects": [
    {
      "field": "chemistry",
      "origin": "openalex:1606|Advanced Physical and Chemical Molecular Interactions",
      "subfield": "physical"
    }
  ],
  "title": "A dimension staircase for orientational heat capacity: nature skips the 3/2 rung",
  "title_text": "A dimension staircase for orientational heat capacity: nature skips the 3/2 rung",
  "type": "preprint",
  "updated_at": "2026-10-30T12:17:24Z",
  "url": "https://research.draconitic.com/paper/aazw2cvzh5wkf",
  "venue": "ChemRxiv",
  "versions": []
}