Optical model with angular-momentum-dependent absorption, exchange of two nucleons, and the scattering of 16O on 18O near the Coulomb barrier

The properties of the optical model with angular-momentum-dependent absorption are studied mainly using the scattering of ¹⁶O on ¹⁸O for energies near the Coulomb barrier. The results have been compared to two-nucleon transfer predictions. The L-dependent form factor has been taken as $f\left(L\right)={1+exp\left[\frac{(L-L_C)}{\Delta L_C}\right]}^{-1}$. The following have been found: (1) There exists an approximate continuous ambiguity concerning the parameters $L_C$ and $\Delta L_C$ which implies a simplification with respect to practical calculations. (2) The L cutoff in the imaginary potential produces an L staggering of the reflection coefficients similar to the one by the exchange model. (3) Both models yield a different energy dependence of the L staggering, since the oscillations of the reflection coefficients are, in the L-dependent optical model, connected with size resonances; in the case of exchange, however, with the symmetry of the reaction and the bound-state wave function of the exchanged particle.[NUCLEAR REACTIONS heavy-ion scattering ¹⁶O on ¹⁸O; two-nucleon exchange; deduced optical model with angular-momentum-dependent absorption.]