The elastic scattering of 104 MeV $\alpha$ particles by ${}_{}{}^{40,42,43,44,48}{}_{}{}^{}\mathrm{Ca}$, ${}_{}{}^{50}{}_{}{}^{}\mathrm{Ti}$, ${}_{}{}^{51}{}_{}{}^{}\mathrm{V}$, and ${}_{}{}^{52}{}_{}{}^{}\mathrm{Cr}$ has been analyzed by phenomenological and semimicroscopic optical potentials in order to get information on isotopic and isotonic differences of the $\alpha$ particle optical potentials and of nuclear matter densities. The phenomenological optical potentials based on a Fourier-Bessel description of the real part reveal different behavior in size and shape for the isotonic chain as compared to the isotopic chain. Odd-even effects are also indicated to be different for isotones and isotopes. The semimicroscopic analyses use a single-folding model with a density-dependent effective $\alpha \mathrm{N}$ interaction including a realistic local density approximation. The calculated potentials are fully consistent with the phenomenological ones. Isotopic and isotonic differences of the nuclear matter densities obtained from the folding model in general show a similar behavior as the optical potential differences. The results on matter densities are compared to other investigations.

• Received 24 October 1983

DOI:https://doi.org/10.1103/PhysRevC.29.1295