Abstract

The total and viscosity cross sections of ³He-³He collisions in HeII are calculated. The basic achievement of the paper is the prediction of the Ramsauer-Townsend effect in this mixture. The RT minimum appears as a result of a balance between attractive short-range and repulsive zero-range interactions. In the low- energy limit the cross sections are dominated by S-wave scattering. In this limit, these cross sections are strongly modified by many-body effects. The influence of S-scattering decreases with increasing pressure and concentration because of the overall repulsion of medium effects.  The effect of the P-wave scattering appears as a resonance-like behavior (peak structure) in the total cross section. This peak structure increases with pressure and concentration. For high energies, these cross sections are independent of pressure and concentration. This indicates that the high-energy behavior is dominated by the self-energy contribution; and the medium effects can be neglected.

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