Measurement of Helium-Helium Scattering Cross Section at Low Temperatures

Abstract

We have measured the${\mathrm{He}}^{4}$-${\mathrm{He}}^{4}$ scattering cross section at 2.1 \ifmmode^\circ\else\textdegree\fi{}K by an atomic-beam method. The value found for the averaged total effective cross section ${\overline{Q}}_{\mathrm{eff}}$ with both beam and scattering gas at 2.1 \ifmmode^\circ\else\textdegree\fi{}K is 144 ${\mathrm{\AA{}}}^{2}$, with an estimated accuracy of 12%. We have also measured the total effective cross section as a function of beam velocity, ${Q}_{\mathrm{eff}}(v)$, with $v$ ranging from 70 m/sec to 210 m/sec. These measurements were made with the scattering gas at 2.1 \ifmmode^\circ\else\textdegree\fi{}K.