Formation of layers and gas and liquid states of helium in 8?13 � diameter pores of Y zeolites

Abstract

Evolution of layers and their motional states for3He and4He adsorbed in Y zeolites have been studied by means of isosteric heat of sorption and heat capacity measurements. The two kinds of Y zeolites used in this study have pores interconnected in a ordered fashion, as well as the same diameter 8–13 A. However, they are different potential profiles on the pore wall. The heat of sorption clearly shows localization potentials at Na+ ion sites on the pore wall for Na-Y zeolites. In contrast, Silica-Y zeolite has few localization sites because it contains very few cations. We find that a solid layer forms on the pore wall at 38% of full pore adsorption amount for both Y zeolites. Upon increasing the amount adsorbed, the adatoms on the solid layer behave as a gas whose molar heat capacity is a half of the gas constant. From 50 to 65 %, the second layer on the pore wall is in a semi-quantum liquid state since the heat capacity becomes proportional to temperature. Finally, the possibility of Fermi degeneracy of adsorbed3He in zeolitic micropores is discussed.