Rotational and vibrational dynamics of interstitial molecular hydrogen

Article

关键词: ORIENTATIONAL ORDERING TRANSITION;    SOLID C-60;    CRYSTAL-STRUCTURE;    CARBON NANOTUBES;    C60;   

DOI  :  10.1103/PhysRevB.66.214301

来源: SCIE

【 摘 要 】

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 H-2 molecules confined to the octahedral interstitial sites of solid C-60. 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 H-2 molecule with a surrounding array of C atoms has not yet been developed.

【 授权许可】

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