${\mathrm{He}}^3$ -Roton Interactions and the Diffusion Constant in ${\mathrm{He}}^3$ -${\mathrm{He}}^4$ Solutions

A microscopic calculation of the scattering cross sections between ${\mathrm{He}}^3$ quasiparticles and rotons in very dilute ${\mathrm{He}}^3$-${\mathrm{He}}^4$ solutions leads to theoretical results on the diffusion constant at high temperatures (∼1.5 K). These results are in good agreement with experiment and demonstrate that the cross sections between elementary excitations in liquid helium are at least in the present case strongly energy dependent.