A NOVEL-APPROACH TO THE OBSERVATION OF THE CONDENSATE FRACTION IN SUPERFLUID-HELIUM 4

We present an analysis of an experiment to observe the condensate frac tion of helium four by firing low-energy pulses of helium atoms at a f inite sample of the superfluid and observing the resulting emission of helium atoms from the fluid. The analysis shows that two kinds of pro cess will result in such emission: in a conventional process in which rotons are produced and propagate to the other side of the droplet, ca using re-emission of helium atoms, the cross-section scales quadratica lly with the geometrical area of the incoming beam. In another process , depending on the existence of the condensate fraction, a lowest-orde r calculation predicts that the cross-section scales with the fourth p ower of the area of the incoming beam. However, a preliminary calculat ion of the matrix elements suggests that the first-order calculation m ay not be adequate for the experimental conditions envisioned. We disc uss possible consequences of this and some experimental considerations regarding the feasibility of observing the effect.