INDEX OF REFRACTION OF NOBLE-GASES FOR SODIUM MATTER WAVES

We present a theoretical study of the index of refraction of the light noble gases He and Ne for the propagation of sodium matter waves. Our approach is based on the well known multiple scattering theory inside a medium, which leads to an approximation for the index of refraction that depends only on the single forward scattering amplitude and the density distribution functions for the atoms of the medium. The forwar d scattering amplitude between a sodium atom and a noble gas atom is c alculated from molecular potential curves using the eikonal approximat ion. An explicit phase space average is performed over the noble gas a tom distribution in the medium. Our results show very good agreement w ith the recent interferometry measurements of Schmiedmayer er al. [Phy s. Rev. Lett. 74, 1043 (1995)]. Our calculations provide an interpreta tion of the experimental data, and may shed some light on possibilitie s for obtaining improved interatomic potentials through atomic interfe rometry measurements.