H2 also has large amplitude motions. Becomes a quantum solid where one can obtain single-photon absorption spectra which would normally be forbidden. Among oth

H2 also has large amplitude motions. Becomes a quantum solid where one can obtain single-photon absorption spectra which would normally be forbidden. Among other very interesting phenomena. https://journals.aps.org/rmp/abstract/10.1103/RevModPhys.52.393 https://journals.aps.org/rmp/abstract/10.1103/RevModPhys.52.... The solid molecular hydrogens in the condensed phase: Fundamentals and static properties Isaac F. Silvera Rev. Mod. Phys. 52, 393 – Published 1 April 1980 "Abstract The molecular hydrogens (H2, D2, HD, etc.) form the simplest of all molecular solids. The combination of the light mass, small moment of inertia, weak interactions, and the quasi-metastable ortho-para species result in a fascinating low-temperature behavior that can be understood to a large extent from considerations of first principles. After discussing single molecule properties and intermolecular interactions we discuss in detail the ortho-para properties, conversion and diffusion. This is followed by a description of the crystal structures and the orientational ordering phenomena. The thermodynamic properties are reviewed. The article is concluded with a discussion of the translational ground state of the solid and the effect of the large zero-point motion on the solid state properties. A large number of data are collected in tables and graphs to provide a reference source."