Structure of helium and neon in zeolite

We have measured the structure of helium and neon adsorbed in zeolite 13X at temperatures in the range 5.5--80 K. No evidence for bulklike liquid or solid behavior is observed for the temperatures studied. Instead, both the He and Ne atoms adsorb into well-defined sites in the zeolite structure. The sites occupied appear to be the same for He and Ne and are consistent with the adsorption sites previously identified for D₂ in 13X. We have also measured the dependence of the structure on pore filling for helium over a limited range of filling.