The total differential cross sections were detd. for the system Na-Ar, Na-Kr, and Na-Xe at thermal energies. All systems show a well resolved oscillation structure of the cross sections. For these data quantum mech. calcns. were performed based on pseudopotentials and calcns. in the elastic WKB approxn. using a Lennard-Jones (8,6) potential. The results allow to det. the interat. potentials with high accuracy. A comparison is made by a detailed listing of exptl. and theor. results published up to now.