title: Phase III of solid methane: the orientational potential and rotational tunneling.
abstract: After many unsuccessful efforts, the structure of solid CD4 III finally has been solved. In this paper, we examine if the known tunneling spectra are consistent with the orientational potentials at the two sites with different symmetries. To this end, we study the rotational kinetic energy of the molecules, construct appropriate pocket states for the tunneling problem, and set up a model potential. Approximate energy levels are obtained from the Ritz variational principle. The agreement between the experimentally determined tunneling frequencies and the calculations is rather good, corroborating the findings of the structural analysis. A continuation of this paper will deal with the partly deuterated methanes.
authors.affiliation: Theory Group, Institut Laue-Langevin, 6 rue Jules Horowitz, F-38042 Grenoble Cedex 9, France.
authors.forename: Alfred
authors.initials: A
authors.lastname: Hüller
authors.forename: Michael
authors.initials: M
authors.lastname: Prager
authors.forename: Werner
authors.initials: W
authors.lastname: Press
authors.forename: Tilo
authors.initials: T
authors.lastname: Seydel