Full angular distributions for elastic and inelastic scattering of 11 B on 58 Ni have been measured at different bombarding energies around the Coulomb barrier. Measurement and analysis with coupled-channel calculations have been performed for the first time for a system with the tightly bound 11 B as projectile on a medium mass target. In these calculations, the real part of the interaction potential between nuclei was represented by a parameter-free double-folding potential. To avoid the use of an imaginary potential at the surface, several inelastic transitions of the projectile and the target have been included in the coupling matrix. The result of these coupled-channel calculations are in very good agreement with all experimental angular distributions. The most important result was the striking influence on the reaction mechanism of the ground-state-spin reorientation of the 11 B nuclei.

Full angular distributions of the 10 B elastically and inelastically scattered by 58 Ni have been measured at different energies around the Coulomb barrier. The elastic and inelastic scattering of 10 B on a medium mass target has been measured for the first time. The obtained angular distributions have been analyzed in terms of large-scale coupled reaction channel calculations, where several inelastic transitions of the projectile and the target, as well as the most relevant one-and two-step transfer reactions have been included in the coupling matrix. The roles of the spin reorientation, the spin-orbit interaction, and the large ground-state deformation of the 10 B, in the reaction mechanism, were also investigated. The real part of the interaction potential between projectile and target was represented by a parameter-free double-folding potential, whereas no imaginary potential at the surface was considered. In this sense, the theoretical calculations were parameter free and their results were compared to experimental data to investigate the relative importance of the different reaction channels. A striking influence of the ground-state spin reorientation of the 10 B nucleus was found, while all transfer reactions investigated had a minimum contribution to the dynamics of the system. Finally, the large static deformation of the 10 B and the spin-orbit coupling can also play an important role in the system studied.

The method of Harper and Hilder is modified to obtain the energy levels of hydrogenic atoms or excitons near hard walls. The method is nonvariational, can be used with two or more bounding surfaces, and gives good results in various cases. It is only required t o know the wave functions in the absence of such surfaces and to perform some elementary integrals.Nous modifions la mkthode de Harper e t Hilder pour obtenir l'irnergie d'atomes hydrogkniques, tels que les excitons, prhs d'une surface rkpulsive. La mkthode n'est pas variationelle e t ne nircessite que les fonctions d'ondes en l'absence des surfaces, ainsi que le calcul de certaines intbgrales 81irmentaires. Nous obtenons pour les cas de une ou deux surfaces des bons rksultats dans tous les cas que nous examinons.The eigenstates of an hydrogenic atom near a hard wall boundary are important to calculate, on several accounts. First, the solutions bear on the properties of excitons near internal or external surfaces of solids; as excitons are created by the absorption of light near a surface, the influence of the surfaces may not be neglected. Second, this problem is simple enough that various techniques may be tested, to see which is best suited for more complex atoms. Thus, the important applications abound in solidstate optical physics as well as in quantum chemistry.The special case of an hydrogen atom, the nucleus of which is located precisely on the boundary wall, is trivially soluble. All the usual eigenstates having a nodal surface which coincides with the physical surface, are allowed, their energy unaltered, in the half-space z > 0. All other eigenstates are discarded. This result was first pointed out by Levine [I], who also noted that the surviving eigenstates all perforce have a dipole moment, that the ionization potential is one-quarter that of the isotropic atom, and many other interesting features too numerous to recapitulate here.Of course, for a nucleus at any finite distance zo from the surface the essential syinnietry is broken and the simplicity of the eigenstates destroyed. Such difficulties, which arise when nonseparable boiindary conditions are imposed on otherwise sirnple equations, were previously noted by Eyges [a] in connection with quantum-mechanical hard spheres. For an exciton or an atom near a hard wall, we have precisely this situation of a rather simple Schrodinger equation subject to Dirichlet boundary conditions on surfaces, the shape of which is incompatible with the natural separation of variables. Even if axial symmetry is retained, the numerical solution of the remaining nonseparable two-dimensional second-order differential equation requires an investment in computational time and effort that is disproportionate with the importance of this problem ; thus, more economical approaches are indicated.

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