The angular distribution between $20°\lesssim {\theta }_{\mathrm{c}.\mathrm{m}.\mathrm{}}\lesssim 180°$ of ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ + ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$ elastic scattering at $E_{\mathrm{c}.\mathrm{m}.\mathrm{}}=35.7\mathrm{}$ MeV has been analyzed in terms of the optical model. For both the real and imaginary parts, the standard Woods-Saxon and spline-function parametrizations of the optical potential have been investigated. In the angular region ${\theta }_{\mathrm{c}.\mathrm{m}.\mathrm{}}\lesssim 112°$, Woods-Saxon—Woods-Saxon potential combinations suffice to describe the data; however, no fit could be obtained either by Woods-Saxon—Woods-Saxon or by Woods-Saxon—Spline-function potentials for the complete angular distribution (${\theta }_{\mathrm{c}.\mathrm{m}.\mathrm{}}\lesssim 180°$). In contrast, the Spline-function—Woods-Saxon combination reproduces the experimental data well. No further improvement of fit quality is obtained by parametrizing both the real and imaginary parts in terms of spline functions. The best-fit Spline-function—Woods-Saxon potential is found to consist of a real part, having significant wiggles in the interior, coupled to a shallow imaginary part with a depth $W\sim 2$ MeV and a large radius $R_i=1.60({A_P}^{\frac{1}{3}}+{A_T}^{\frac{1}{3}})$ fm.

NUCLEAR REACTIONS ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ + ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$ elastic scattering, $E_{\mathrm{c}.\mathrm{m}.\mathrm{}}=35.7\mathrm{}$ MeV; optical model analysis including a "model-independent" potential parametrization by spline functions.

• Received 6 April 1981

DOI:https://doi.org/10.1103/PhysRevC.24.966