Comparison of Strengths of Trapping of Helium in the Solid and Liquid State of Hydrogen

Alok Nandini Usha Roy (SUNY Albany, Albany NY), R. H. Scheicher, T. P. Das (SUNY Albany), K. Ishida (RIKEN, Wako-shi, Japan), T. Matsuzaki, S. N. Nakamura, N. Kawamura (RIKEN), K. Nagamine (KEK-MSL, Tsukuba, Japan; RIKEN)

Using the first-principles Hartree-Fock Cluster procedure, and incorporating many-body effects, we have investigated the trapping of He+ at the tetrahedral and octahedral interstitial sites in solid hydrogen. The binding energies of He+ were found to increase significantly when second-nearest neighbor H2 molecules were included in the calculation as compared to the case when only first-nearest neighbors were present. Expanding the cluster to include third-nearest neighbors, we found good convergence in the binding energy of He+. These results can be taken as evidence that He+ is trapped more strongly in solid hydrogen than in the liquid, as suggested by recent data from Muon Catalyzed Fusion experiments (N. Kawamura et al., Phys. Lett. B465), 74 (1999). Possible implications for the trapping of other helium entities (e.g. He0 or (He-H)+) will be discussed.

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