ATOMIC IMPACT EXPERIMENTS WITH FREE HE-3 AND HE-4 CLUSTERS

Free helium clusters with of the order of 10(3) to 10(7) atoms have be en predicted to reach final temperatures of about 0.4 K in the case of He-4, and of 0.15 K in the case of He-3. In the first case, the clust ers have to be expected to be superfluid, in the latter case to be nor malfluid. Impact experiments with cesium atoms, which are calculated t o be strongly repelled from inside liquid He-4, and slightly from liqu id He-3, indicate cesium embedding into or onto He-4 clusters. Xenon a toms, calculated to be strongly bound to both quantum liquids, show in complete momentum transfer to He-4 as well as to He-3 clusters at high er impact speeds.