Experimental evidence for the transmission of He-3 atoms through superfluid He-4 droplets

The momentum and energy transferred to large, cold (0.38 K) superfluid He-4 droplets ((N) over bar = 1.5 x 10(9) atoms) in low energy (5-10 K) collisi ons with He-3 and He-4 atoms were determined from time-of-flight and mass s pectrometer measurements. At the lowest total collision energies, He-3 atom s transfer only 45% of their momentum and 60% of their energy, whereas He-4 atoms transfer 65% of their momentum and 100% of their energy. These resul ts are consistent with He-3 atoms being transmitted through the superfluid droplets, while in the case of He-4 atoms some of the momentum is transmitt ed via phonon mechanisms.