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Determination of the Interval between the Ground States of Para- and Ortho-H2

M. Beyer, N. Hölsch, J. Hussels, C.-F. Cheng, E. J. Salumbides, K. S. E. Eikema, W. Ubachs, Ch. Jungen, and F. Merkt
Phys. Rev. Lett. 123, 163002 – Published 16 October 2019
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Abstract

Nuclear-spin-symmetry conservation makes the observation of transitions between quantum states of ortho- and para-H2 extremely challenging. Consequently, the energy-level structure of H2 derived from experiment consists of two disjoint sets of level energies, one for para-H2 and the other for ortho-H2. We use a new measurement of the ionization energy of para-H2 [EI(H2)/(hc)=124417.491098(31)cm1] to determine the energy separation [118.486770(50)cm1] between the ground states of para- and ortho-H2 and thus link the energy-level structure of the two nuclear-spin isomers of this fundamental molecule. Comparison with recent theoretical results [M. Puchalski et al., Phys. Rev. Lett. 122, 103003 (2019)] enables the derivation of an upper bound of 1.5 MHz for a hypothetical global shift of the energy-level structure of ortho-H2 with respect to that of para-H2.

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  • Received 18 July 2019

DOI:https://doi.org/10.1103/PhysRevLett.123.163002

© 2019 American Physical Society

Physics Subject Headings (PhySH)

Atomic, Molecular & Optical

Authors & Affiliations

M. Beyer1,*, N. Hölsch1, J. Hussels2, C.-F. Cheng2,†, E. J. Salumbides2, K. S. E. Eikema2, W. Ubachs2, Ch. Jungen3, and F. Merkt1

  • 1Laboratorium für Physikalische Chemie, ETH Zürich, 8093 Zürich, Switzerland
  • 2Department of Physics and Astronomy, LaserLaB, Vrije Universiteit Amsterdam, de Boelelaan 1081, 1081 HV Amsterdam, Netherlands
  • 3Department of Physics and Astronomy, University College London, London WC1E 6BT, United Kingdom

  • *Present address: Department of Physics, Yale University, New Haven, CT 06520, USA.
  • Permanent address: Hefei National Laboratory for Physical Sciences at Microscale, iChem center, University of Science and Technology China, Hefei 230026, China.

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Issue

Vol. 123, Iss. 16 — 18 October 2019

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