THE ROLE OF ROTON BACKFLOW IN QUANTUM EVAPORATION FROM HELIUM-II

We have developed a real space Beliaev [5] theory which includes a nov el semi-phenomenological roton backflow effect in order to examine the effect of backflow on the Quantum Evaporation of atoms from the super fluid helium surface by rotons in the liquid. The resulting equations are solved within a local density approximation and we examine the WKB solutions in order to compare the results with a previous theory of M ulheran and Inkson [3] in which the backflow is neglected. It is found that the backflow has a significant but not dominant effect and that its inclusion will improve agreement with experiment in a full numeric al study.