Atomic impact experiments with free helium-3 and helium-4 clusters

Abstract

Free helium clusters with of the order of 103 to 107 atoms have been predicted to reach final temperatures of about 0.4 K in the case of4He, and of 0.15 K in the case of3He. In the first case, the clusters have to be expected to be superfluid, in the latter case to be normalfluid. Impact experiments with cesium atoms, which are calculated to be strongly repelled from inside liquid4He, and slightly from liquid3He, indicate cesium embedding into or onto4He clusters. Xenon atoms, calculated to be strongly bound to both quantum liquids, show incomplete momentum transfer to4He as well as to3He clusters at higher impact speeds.