Heat capacity and torsional oscillator studies of molecular hydrogen in porous Vycor glass

Abstract

We have measured the heat capacity of para-hydrogen in a series of samples of porous Vycor glass at temperatures in the range 0.6 to 12 K. For hydrogen in the samples with large pores a freezing transition is observed; in the small-pore samples there is no feature that can be associated with a liquid-solid transition. At low temperatures the heat capacity of hydrogen in Vycor is found to decrease as the amount of hydrogen in the pores increases. We discuss possible explanations for this behavior. For hydrogen in small-pore Vycor we have made a search for superfluidity down to 0.08 K. No sharp transition is observed down to this temperature.