Airy structure in16O+16Oelastic scattering between 5 and 10 MeV/nucleon

Abstract

We have applied the barrier-wave/internal-wave decomposition technique to ${}^{16}\mathrm{O}{+}^{16}\mathrm{O}$ elastic scattering optical model angular distributions between 75 and 145 MeV, an energy region where strong refractive effects---in particular Airy maxima and minima---are clearly observed; this technique, introduced in a semiclassical framework more than 20 years ago by Brink and Takigawa, and which was successful in clarifying the light-ion elastic scattering mechanism, has practically never been used in the context of light heavy-ion scattering. The decomposition is accomplished by using a fully quantum-mechanical method, which bypasses the intricacies of the semiclassical approach. The Airy minima are found to be due to the interference of the barrier-wave and internal-wave subamplitudes; the presence of a substantial internal-wave contribution demonstrates in a very clear way the exceptional transparency displayed by the ${}^{16}\mathrm{O}{+}^{16}\mathrm{O}$ system. The results obtained contrast with those of the nearside/farside decomposition technique, where the Airy minima are fully carried by the farside contribution. By combining the two approaches it is possible to calculate in a straightforward way the two components underlying the structure of the farside component, which up to now have been obtained through delicate semiclassical calculations or the use of an approximate empirical method. The complicated evolution of the full elastic cross section can eventually be explained in terms of the interference of several subamplitudes with a much smoother, and thus much simpler to understand, behavior. A barrier-wave/internal-wave decomposition of the 132 MeV ${}^{16}\mathrm{O}{+}^{12}\mathrm{C}$ and 100 MeV ${}^{18}\mathrm{O}{+}^{12}\mathrm{C}$ elastic scattering amplitudes is also presented.