Relative evaporation probabilities of He-3 and He-4 from the surface of superfluid He-4

We report a preliminary experiment which demonstrates that He-3 atoms in An dreev states are evaporated by high-energy (E/kappa(B) = 10.2 K) phonons in a quantum evaporation process similar to that which occurs in pure He-4. U nder conditions of low He-3 coverage, high-energy phonons appear to evapora te He-3 and 4He atoms with equal probability. However, we have not managed to detect any He-3 atoms that have been evaporated by rotons, and conclude that the probability of a roton evaporating a He-3 atom is less than 2% of the probability that it evaporates a He-4 atom. (C) 2000 Elsevier Science B .V. All rights reserved.