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

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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC10497966PMC
http://dx.doi.org/10.3389/fchem.2023.1258035DOI Listing

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