In a crossed molecular beam experiment, timehyphen;ofhyphen;flight distributions of HD molecules scattered from D2have been measured at 42.2, 45.4, and 50.8 meV collision energy using the pseudorandom chopper method. In all cases rotational transitions of HD fromj=0 toj=1 were resolved. At 45.4 meV complete differential cross sections have been generated from 10thinsp;deg; to 120thinsp;deg;. They display well resolved diffraction oscillations in both the elastic 0rarr;0 and inelastic 0rarr;1 channels. Calculations show that these data essentially provide information on the position and the slope of the isotropic H2ndash;H2interaction potential near the zero point. The comparison between measurement and close coupling calculations based on theabinitiopotential surface of Meyer and Schaefer shows a remarkable agreement. Only very small deviations in the positions of the diffraction oscillation extrema occur giving rise to a slight modification of the repulsive wall near the zero point. It has to be shifted by 0.1 Aring; to give a perfect fit to the measured data.
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