ATOMIC AND MOLECULAR-HYDROGEN IMPURITIES IN LIQUID-HE-4

The static properties of a single hydrogen atom and an hydrogen molecu le in bulk superfluid He-4 are studied by means of the diffusion Monte Carlo method. The analysis includes atomic hydrogen, deuterium and tr itium, and molecular hydrogen and deuterium. Our results, which show s ome differences with previous variational calculations, are in agreeme nt with the only available experimental data corresponding to atomic d euterium. In contrast to the unbinding presented by the atomic impurit ies, the molecular ones do bind with energies higher than the chemical potential of pure He-4.