{
  "abstract": "The azide ion (N 3 - ) is a highly sensitive vibrational probe for investigating ion–pair interactions in solution. In dimethylsulfoxide (DMSO), N 3 - forms contact ion pairs with cations, leading to two distinct asymmetric stretching bands in the Fourier transform infrared (FT-IR) spectrum. Although this seems obvious, distinguishing different ion-pair species in detail becomes challenging because vibrational features overlap in the linear IR spectra. To obtain more insight into this apparent complexity, we employed two-dimensional correlation spectroscopy (2D-COS) in combination with molecular dynamics (MD) simulations to precisely distinguish the overlapping ion-pair species. Complementing the structural information from IR spectroscopy we used soft X-ray absorption spectroscopy (XAS) at the N K-edge to reveal the electronic interactions underlying the ion-pairing and to distinguish the effect of counter-ions on each atom of N 3 - separately. Combined with calculated spectra, our study demonstrates that nitrogen K-edge XAS, by probing transitions of nitrogen 1s core electrons to unoccupied molecular orbitals, directly reflects how the local electronic structure of N 3 - is affected by ion pairing. We provide evidence, in particular, for ion pairing results due to hybridization of unoccupied orbitals of N 3 - with valence orbitals of the adjacent Na + and Ca 2+ cations.",
  "abstract_shown": true,
  "affiliations": [
    "Max Born Institute for Nonlinear Optics & Short Pulse Spectroscopy, Max Born Str. 2A, Berlin, Germany, 12489",
    "Department of Physics",
    "Stockholm University, AlbaNova University Center",
    "Institut für Chemie",
    "Martin-Luther-Universität Halle-Wittenberg",
    "Department of Physics and Astronomy",
    "Uppsala University",
    "Institute for Methods and Instrumentation for Synchrotron Radiation Research",
    "Helmholtz-Zentrum Berlin für Materialien und Energie GmbH"
  ],
  "article_type": null,
  "arxiv": null,
  "author_total": 12,
  "authors": [
    {
      "affs": [
        0
      ],
      "name": "Debkumar Rana"
    },
    {
      "affs": [
        1,
        2
      ],
      "name": "Sambit K. Das"
    },
    {
      "affs": [
        3,
        4
      ],
      "name": "Anna Luisa Upterworth",
      "orcid": "0009-0003-0677-8745"
    },
    {
      "affs": [
        0
      ],
      "name": "Marc-Oliver Winghart"
    },
    {
      "affs": [
        0
      ],
      "name": "Mate Kurucz"
    },
    {
      "affs": [
        5,
        6
      ],
      "name": "Victoria Kabanova"
    },
    {
      "affs": [
        7,
        8
      ],
      "name": "Sebastian Eckert"
    },
    {
      "affs": [
        7,
        8
      ],
      "name": "Mattis Fondell"
    },
    {
      "affs": [
        5,
        6
      ],
      "name": "Philippe Wernet"
    },
    {
      "affs": [
        3,
        4
      ],
      "name": "Daniel Sebastiani"
    },
    {
      "affs": [
        1,
        2
      ],
      "name": "Michael Odelius"
    },
    {
      "affs": [
        0
      ],
      "name": "Erik T. J. Nibbering"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/40wxx40dr5w07.bib",
  "cited_by": 0,
  "doi": "10.26434/chemrxiv.15010366/v1",
  "fulltext_url": null,
  "id": "40wxx40dr5w07",
  "issns": [],
  "landing_url": "https://chemrxiv.org/doi/full/10.26434/chemrxiv.15010366/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",
      "3107|Spectroscopy and Quantum Chemical Studies"
    ]
  ],
  "openalex": "W7221603831",
  "pdf_url": "https://chemrxiv.org/doi/pdf/10.26434/chemrxiv.15010366/v1",
  "pmcid": null,
  "pmid": null,
  "published": "2026-10-13",
  "publisher": "American Chemical Society (ACS)",
  "ris": "https://research.draconitic.com/paper/40wxx40dr5w07.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:17:24Z",
      "native_id": "10.26434/chemrxiv.15010366",
      "source": "chemrxiv",
      "url": "https://chemrxiv.org/doi/full/10.26434/chemrxiv.15010366/v1"
    }
  ],
  "subjects": [
    {
      "field": "physics",
      "origin": "openalex:3107|Spectroscopy and Quantum Chemical Studies",
      "subfield": "amo"
    }
  ],
  "title": "Probing the vibrational and electronic structures of azide contact ion pairs in DMSO with fourier-transform infrared and soft x-ray absorption spectroscopy",
  "title_text": "Probing the vibrational and electronic structures of azide contact ion pairs in DMSO with fourier-transform infrared and soft x-ray absorption spectroscopy",
  "type": "preprint",
  "updated_at": "2026-10-30T12:17:24Z",
  "url": "https://research.draconitic.com/paper/40wxx40dr5w07",
  "venue": "ChemRxiv",
  "versions": []
}