Mobility of negative ions in superfluid 3He

The experimentally measured mobility of negative ions in liquid 3He remains remarkably constant down to the superfluid transition temperature, and then rises rapidly with dropping temperature in the superfluid phases. In this report, the reasons of the constancy of the normal state mobility and of the rapid rise in the superfluid phases are considered on the basis of cross sections and the number of thermally excited quasiparticles. The equation for the mobility in the quasi-isotropic B phase is given as a function of the quasiparticle energy and the transport cross section for scattering of a 3He quasiparticle by an ion at rest. In the superfluid phases, the mobility is increased due to the reduction in the number of thermally excited quasiparticles, and to the reduction of the transport cross section with energy. Differential quasiparticle-ion cross section in the B phase is presented, taking the ratio of energy in normal to superfluid states as the parameter. Another figure shows the spin averaged transport and total cross sections for 3He quasiparticle-ion scattering in the B phase. (Aoki, K