Evolution of layers and motional states of helium adatoms in the micro-pores of Y zeolites

Abstract

Properties of helium adatoms in the 8–13A˚diameter pores of Na-Y and Silica-Y zeolites with different Si/Al ratios and cations have been studied by measuring an isosteric heat q st of adsorption and heat capacity C. Step-wise changes of q st at T=0K with increasing the amount n adsorbed give magnitudes of the localization potentials on the pore wall and they show evolution of layers. In the Y zeolites, a first layer is completed at n∼38% of the full pore amount. The adatoms on the first layer are gas-like since we observed ∂C/∂n∼R/2 (=4.2J/K/mol) at 38< n≲45% and 1≲T≲5K. At 50≲n≲65%, they are liquid-like state with a T-linear heat capacity. Fermi degeneracy of the gas- or liquid-like 3He adatoms is possible below a few hundreds mK.