The diffusion cross section for atomic hydrogen in helium gas at low temperature and the HHe potential

A calculation of the diffusion cross section Q D of hydrogen atoms in helium gas at low temperature is performed and compared with recent experimental results. The comparison allows an improved determination of the H–He potential. Calculations were done for three different potentials: our own empirical potential based on experimental high-energy scattering results and calculated long-range dispersion terms, which gives good results for Q D and total collision cross sections; a recently determined semi-empirical potential, and an ab initio calculated potential. All three potentials imply a strong temperature dependence of Q D for T < 1.5 K.