Dissipation mechanisms near the superfluid 3He transition in aerogel.

We have investigated the dissipation (Q - 1 ) using the torsion pendulum technique for pure 3 He and 3 He- 4 He mixtures in silica aerogel near the 3 He superfluid transition (T c ) in aerogel. With pure 3 He the Q - 1 decreases at the onset of superfluidity. When phase separated 3 He- 4 He mixtures are introduced into the aerogel, the Q - 1 does not decrease as rapidly and eventually increases for the highest 4 He content. We provide a model for the related attenuation of transverse sound a that takes into account elastic and inelastic scattering processes and exhibits a decrease in a at T c .