Mechanical responses of helium films adsorbed on two-dimensional mesoporous hectorite

The mechanical responses of physisorbed films to the vibration of a substra te were investigated by measuring the sound velocity and attenuation of a t wo-dimensional mesoporous hectorite. The sound velocity of a hectorite pell et adsorbed by both He-4 and He-3 submonolayer films increased drastically at low temperatures accompanied by the attenuation. The most plausible expl anation for this behavior is that helium films decouple from the vibrating substrate at low temperatures. (C) 1999 Elsevier Science B.V. All rights re served.