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ABSTRACT For decades, protonated methane, CH5+, has provided new surprises and challenges for both experimentalists and theoreticians. This is because of the correlated large-amplitude

motion of its five protons around the carbon nucleus, which leads to so-called hydrogen scrambling and causes a fluxional molecular structure. Here, the infrared spectra of all its H/D

isotopologues have been measured using the ‘Laser Induced Reactions’ technique. Their shapes are found to be extremely dissimilar and depend strongly on the level of deuteration (only CD5+

is similar to CH5+). All the spectra can be reproduced and assigned based on _ab initio_ quantum simulations. The occupation of the topologically different sites by protons and deuterons is

found to be strongly non-combinatorial and thus non-classical. This purely quantum-statistical effect implies a breaking of the classical symmetry of the site occupations induced by

zero-point fluctuations, and this phenomenon is key to understanding the spectral changes studied here. Access through your institution Buy or subscribe This is a preview of subscription

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CARBON NUCLEUS Article Open access 15 May 2023 CONDENSED-PHASE ISOMERIZATION THROUGH TUNNELLING GATEWAYS Article Open access 20 October 2022 FACTORS GOVERNING \({\RM H}_{3}^{+}\) FORMATION

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ACKNOWLEDGEMENTS The Bochum group is grateful to H. Forbert for useful discussions and technical help and is supported by Deutsche Forschungsgemeinschaft (DFG) (Normalverfahren MA 1547/4)

and Fonds der Chemischen Industrie (FCI) (Chemiefonds–Stipendium to A.W. and general grant to D.M.). The simulations were carried out at HLRB II (München), Bovilab@RUB (Bochum) and

Rechnerverbund–NRW (Dortmund). The Köln group gratefully acknowledges the help of their mechanical workshop (J. Krause, D. Moratschke and their team) as well as FOM for providing beam time.

The skilful assistance provided by the Felix staff is greatly appreciated. Financial support by DFG through SFB 494 and the European QUASAAR network and the Initiative ‘Integrating Activity

on Synchrotron and Free Electron Laser Science’ is also acknowledged. AUTHOR INFORMATION Author notes * Gerald Mathias Present address: Present address: Lehrstuhl für BioMolekulare Optik,

Ludwig–Maximilians–Universität, Oettingenstrasse 67, 80538 München, Germany, * Sergei D. Ivanov and Oskar Asvany: These authors contributed equally to this work AUTHORS AND AFFILIATIONS *

Lehrstuhl für Theoretische Chemie, Ruhr-Universität Bochum, Bochum, 44780, Germany Sergei D. Ivanov, Alexander Witt, Gerald Mathias & Dominik Marx * I. Physikalisches Institut,

Universität zu Köln, Zülpicher Strasse 77, Köln, 50937, Germany Oskar Asvany, Edouard Hugo & Stephan Schlemmer * Felix Facility, FOM–Institute for Plasma Physics ‘Rijnhuizen’,

Nieuwegein, 3430 BE, The Netherlands Britta Redlich Authors * Sergei D. Ivanov View author publications You can also search for this author inPubMed Google Scholar * Oskar Asvany View author

publications You can also search for this author inPubMed Google Scholar * Alexander Witt View author publications You can also search for this author inPubMed Google Scholar * Edouard Hugo

View author publications You can also search for this author inPubMed Google Scholar * Gerald Mathias View author publications You can also search for this author inPubMed Google Scholar *

Britta Redlich View author publications You can also search for this author inPubMed Google Scholar * Dominik Marx View author publications You can also search for this author inPubMed 

Google Scholar * Stephan Schlemmer View author publications You can also search for this author inPubMed Google Scholar CONTRIBUTIONS D.M. and S.S. designed the research. O.A., E.H., B.R.

and S.S. performed the experiments. S.D.I. and A.W. performed the calculations. S.D.I., O.A., A.W., G.M., D.M. and S.S. analysed the data. S.D.I., O.A., A.W., D.M. and S.S. wrote the paper.

CORRESPONDING AUTHORS Correspondence to Sergei D. Ivanov or Oskar Asvany. ETHICS DECLARATIONS COMPETING INTERESTS The authors declare no competing financial interests. SUPPLEMENTARY

INFORMATION SUPPLEMENTARY INFORMATION Supplementary information (PDF 1542 kb) RIGHTS AND PERMISSIONS Reprints and permissions ABOUT THIS ARTICLE CITE THIS ARTICLE Ivanov, S., Asvany, O.,

Witt, A. _et al._ Quantum-induced symmetry breaking explains infrared spectra of CH5+ isotopologues. _Nature Chem_ 2, 298–302 (2010). https://doi.org/10.1038/nchem.574 Download citation *

Received: 29 September 2009 * Accepted: 18 January 2010 * Published: 28 February 2010 * Issue Date: April 2010 * DOI: https://doi.org/10.1038/nchem.574 SHARE THIS ARTICLE Anyone you share

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