Rotational and Vibrational Dynamics of Interstitial Molecular Hydrogen

Thumbnail Image
Penn collection
Department of Physics Papers
Degree type
Quantum Physics
Grant number
Copyright date
Related resources

The calculation of the hindered roton-phonon energy levels of a hydrogen molecule in a confining potential with different symmetries is systematized for the case when the rotational angular momentum J is a good quantum number. One goal of this program is to interpret the energy-resolved neutron time-of-flight spectrum previously obtained for H2C60. This spectrum gives direct information on the energy-level spectrum of H2 molecules confined to the octahedral interstitial sites of solid C60. We treat this problem of coupled translational and orientational degrees of freedom (i) by construction of an effective Hamiltonian to describe the splitting of the manifold of states characterized by a given value of J and having a fixed total number of phonon excitations, (ii) by numerical solutions of the coupled translation-rotation problem on a discrete mesh of points in position space, and (iii) by a group theoretical symmetry analysis. Results obtained from these three different approaches are mutually consistent. The results of our calculations explain several aspects of the experimental observations, but show that a truly satisfactory orientational potential for the interaction of an H2 molecule with a surrounding array of C atoms has not yet been developed.

Date Range for Data Collection (Start Date)
Date Range for Data Collection (End Date)
Digital Object Identifier
Series name and number
Publication date
Journal title
Physical Review B
Volume number
Issue number
Publisher DOI
Journal Issue
At the time of publication, authors Taner Yildirim and A. Brooks Harris were affiliated with the National Institute of Standards and Technology, Gaithersburg, Maryland. Currently, they are faculty members in the Materials Science and Engineering and Physics Departments, respectively, at the University of Pennsylvania.
Recommended citation