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) collisions with He-3 and He-4 atoms were determined from time-of-flight and mass spectrometer measurements. At the lowest total collision energies, He-3 atoms 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 results 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 transmitted via phonon mechanisms.