Long Range Potential Effects in Low Density Krypton Gas

Small angle neutron scattering (SANS) in low density ⁸⁶Kr gas has been performed in order to measure the small- k behavior of the static structure factor $S(k)$. Three number densities between 1.52 and 2.42nm^-3 along the T0ex0ex=0ex0ex297K isotherm have been studied. The small- k dependence of the Fourier transform $c(k)$ of the direct correlation function $c(r)$ has been derived. The experimental determination of the k³ term in the behavior of $c(k)$ has led to a direct measurement of the London dispersion interaction in the pair potential of krypton. Also the contribution of the three-body potential in the asymptotic behavior of $c(r)$ has been observed and related to the magnitude of the three-body interaction potential.