Remarks on the proximity scaling applied to heavy ion interaction potentials

Two heavy ion interaction potentials have been computed using the same nuclear force. One has been obtained from symmetric semi-infinite nuclear matter slabs and the other one from finite nuclei. After a proximity scaling, two rather different universal functions are obtained. We argue that this is due to the different surface thickness of semi-infinite nuclear matter and finite nuclei. Consequently, it is the universal function obtained from the nucleus-nucleus systematics that should be used in the applications