TOTAL DIFFERENTIAL SCATfERING CROSS SECTION OF Ar+-Ar AT 15 TO 400 keV

Knowledge of the potential energy surfaces of a molecule is the key to the interpretation of many molecular properties. The same statement holds true for a quasi-molecule formed during a scattering process, where the knowledge of allpotential energy curves for all excitations plus knowledge of the connecting matrix elements between these channels would, in principle, allow a complete description of the scattering process. Because the potential energy curves play such an important role in molecules as well as quasi-molecules, their determination is one ofthe main theoretical as well as experimental tasks. The theoretical difficulty in calculating a realistic potential energy surface is, of course, the complexity of the many-particle problem which, in addition, has to include relativity for heavy systems. Quantum chemists are now able to determine potential energy surfaces for many systems and many excitations with great accuracy. An almost complete list of references is given in the book by Schaefer 111 [1]. Their methods, however, are onIy suitable for small Z systems and for intemuclear distances in the range of chemical distances or larger. For light as well as heavy systems the region just below chemical distances is a field where our knowledge is still very limited. The aim of this letter is to