{
  "abstract": "Helium scattering measures the coherent intermediate scattering function of an adlayer, the characteristic function of the separation between adparticles at two times. Published dephasing rates of H and D on Pt(111) are analysed with its memory equation and a nearest-neighbour Ising lattice gas. The measured rate belongs to the adlayer. The hop rate of a single adsorbate is extracted from it by dividing out an interaction factor, without a model of the barrier. This factor lies between $0.97$ and $1.17$ at $0.1$~ML, so that the published single-adsorbate analyses hold there. At $0.4$~ML and $80$~K it lies between $1.2$ and $4.7$, depending on how the occupied neighbours modify a tunnelling jump. The memory function is interpreted as a friction, the collective friction, which the adlayer exerts on its own density fluctuations. The lateral coupling, fixed by the coverage series, is the free energy of a neighbouring pair, with a vibrational pair entropy. The small deformation of the measured curves from the Chudley--Elliott form, the tilt, is proposed as an observable of the coupling. The tilts at $0.15$ and $0.2$~ML are consistent with it, although they are hard to extract from the published curves. The memory equation provides a transition-state theory for the adlayer, with the collective friction in the role of the friction of the substrate and without divergence at the crossover. Combined with the standard quantum transition-state theory of a single adsorbate, the extracted hop rates give the friction of the substrate, $124$ and $75$~ps$^{-1}$ for H and D, independent of the coverage.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2610.39436",
  "author_total": 1,
  "authors": [
    {
      "name": "S. Miret-Artés"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/ehjs5nvs918hh.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2610.39436",
  "fulltext_url": null,
  "id": "ehjs5nvs918hh",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2610.39436",
  "language": null,
  "licence": "LicenseRef-arXiv-nonexclusive-1.0",
  "licence_label": "arXiv licence",
  "licence_source": "article",
  "licence_url": "http://arxiv.org/licenses/nonexclusive-distrib/1.0/",
  "metadata_licence": "CC0-1.0",
  "native_subjects": [
    [
      "arxiv",
      "cond-mat.stat-mech"
    ]
  ],
  "openalex": null,
  "pdf_url": "https://arxiv.org/pdf/2610.39436",
  "pmcid": null,
  "pmid": null,
  "published": "2026-10-29",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/ehjs5nvs918hh.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:36:23Z",
      "native_id": "2610.39436",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2610.39436"
    }
  ],
  "subjects": [
    {
      "field": "physics",
      "origin": "arxiv:cond-mat.stat-mech",
      "subfield": "statistical-nonlinear"
    }
  ],
  "title": "Hop rates of H and D on Pt(111) at finite coverage: the memory equation and the collective friction",
  "title_text": "Hop rates of H and D on Pt(111) at finite coverage: the memory equation and the collective friction",
  "type": "preprint",
  "updated_at": "2026-11-01T12:20:45Z",
  "url": "https://research.draconitic.com/paper/ehjs5nvs918hh",
  "venue": "arXiv",
  "versions": []
}