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Abstract   We have studied heat capacities of 4He adsorbed in straight nanopores 1.8, 2.2, and 2.8 nm in diameter. Heat capacities of the 4He fluid film on the solid layer at 0.08–0.4 K show power laws close to T in 1.8 nm pores, close to T 2 in 2.8 nm pores, and a crossover from T to T 2 with increasing temperature in 2.2 nm pores. These heat capacities are explained by a model assuming a phonon dispersion with continuous one-dimensional (1D) states in the axial direction and discrete energy levels in the azimuthal direction. By fitting experimental data to the model, the phonon velocity along the pore axis and the energy gap for propagation in the cross section are derived. At temperatures sufficiently lower than the energy gap, where the thermal wave length of phonons is much longer than the effective pore diameter, the 4He fluid films show a T-linear heat capacity of 1D phonons propagating only along the pore axis. At higher temperatures, a 1D-2D crossover of phonons occurs. [ABSTRACT FROM AUTHOR]

Abstract   We have measured the heat capacity of 3He adsorbed on three-dimensionally connected nanopores, 2.7 nm in diameter, preplated with about 1.3 atomic layers of 4He. At low coverages of 3He, the 3He heat capacity is roughly constant at the measured temperatures between 0.1 and 1 K. Its molar heat capacity is on the order of the gas constant R, between 1.1R and 1.8R. This suggests a Boltzmann gas state of the adsorbed 3He. At high coverages, the heat capacity is likely approaching linear in T at low temperatures, which suggests a degenerate state at further lower temperatures. [ABSTRACT FROM AUTHOR]

No Heading We have measured the heat capacity of 3He adsorbed on one-dimensional (1D) nanopores of FSM-16 with different pore-diameters. Dilute 3He atoms on more than one layers of 4 He preplated nanotunnels with 22 Å in diameter show a Schottky type peak around 0.25 K, which is similar to our recent report for 28 Å nanotunnels. This behavior of heat capacity is explained as the crossover from 1D to 2D motion of Fermi gas in a confined geometry. The pore-size effect on the temperature and magnitude of the peak is quantitatively reproduced by a simple calculation for non-interacting Fermi gas in the adsorption potential from the substrate. [ABSTRACT FROM AUTHOR]