Fast ortho-to-para conversion of molecular hydrogen in chemisorption and matrix-isolation systems

Hirokazu Ueta; Katsuyuki Fukutani; Koichiro Yamakawa

doi:10.3389/fchem.2023.1258035

Fast ortho-to-para conversion of molecular hydrogen in chemisorption and matrix-isolation systems

Front Chem. 2023 Aug 29:11:1258035. doi: 10.3389/fchem.2023.1258035. eCollection 2023.

Authors

Hirokazu Ueta¹, Katsuyuki Fukutani^{1

2}, Koichiro Yamakawa¹

Affiliations

¹ Advanced Science Research Center, Japan Atomic Energy Agency, Ibaraki, Japan.
² Institute of Industrial Science, The University of Tokyo, Tokyo, Japan.

Abstract

Molecular hydrogen has two nuclear-spin modifications called ortho and para. Because of the symmetry restriction with respect to permutation of the two protons, the ortho and para isomers take only odd and even values of the rotational quantum number, respectively. The ortho-to-para conversion is promoted in condensed systems, to which the excess rotational energy and spin angular momentum are transferred. We review recent studies on fast ortho-to-para conversion of hydrogen in molecular chemisorption and matrix isolation systems, discussing the conversion mechanism as well as rotational-relaxation pathways.

Keywords: adsorption; hydrogen; matrix isolation; nuclear spin; rotational energy; surface.

Publication types

Review

Grants and funding

The authors declare financial support was received for the research, authorship, and/or publication of this article. This work was supported by the Japan Society for the Promotion of Science (KAKENHI; Grant JP18H05518, JP20K05424, JP20K05337, JP21H04650, JP23H01856, and JP23K04593) and Grant for Basic Science Research Projects from the Sumitomo Foundation. HU was partially supported by MEXT Japan, Leading Initiative for Excellent Young Researchers.