Modeling $\alpha$-nucleus elastic scattering using a velocity-dependent optical potential

We performed a least-squares fit analysis to reproduce the elastic angular distributions for $\alpha$ scattering on various nuclei form ${}^{12}\mathrm{C}$ to ${}^{208}\mathrm{Pb}$ for incident energies in the range 18–70 MeV using a velocity-dependent optical model (VDOM). The model reproduced the experimental data well including the enhanced angular distributions in the large-angle scattering region, which is commonly known as the anomalous large angle scattering (ALAS). Our best-fit potential parameters are linear functions of incident energy. Although the ALAS effect is not present in the case of $\alpha$ scattering on the medium mass ${}^{58}\mathrm{Ni}$ and heavy mass ${}^{208}\mathrm{Pb}$ nuclei, we considered these nuclei to demonstrate the effectiveness of the VDOM in describing the angular distributions for $\alpha$ scattering on various light, medium, and heavy mass nuclei. For $\alpha$ scattering on ${}^{40}\mathrm{Ca}$, we compared our results to two previous works that adopted the conventional optical model. One model reproduced the data better at low energies, while the other performed better at high energies. In contrast, the velocity-dependent model of this work described the data across the considered angular range.

Figure 1

Our best angular distribution fits for $\alpha$ scattering on ${}^{12}\mathrm{C}$ obtained using the velocity-dependent optical model (VDOM).

Figure 2

Our best angular distribution fits for $\alpha$ scattering on ${}^{16}\mathrm{O}$ obtained using the velocity-dependent optical model (VDOM).

Figure 3

Our best angular distribution fits for $\alpha$ scattering on ${}^{40}\mathrm{Ca}$ obtained using the velocity-dependent (VDOM) and conventional optical (COM) models.

Figure 4

Our best angular distribution fits for $\alpha$ scattering on ${}^{40}\mathrm{Ca}$ obtained using the velocity-dependent optical model (VDOM) compared to those obtained using the convention optical model (COM) of the works Delbar et al. [46] and Michel et al. [47].

Figure 5

Our best angular distribution fits for $\alpha$ scattering on ${}^{40}\mathrm{Ca}$ obtained using the velocity-dependent optical model (VDOM) compared to those obtained using the convention optical model (COM) of the works Delbar et al. [46] and Michel et al. [47].

Figure 6

Our best angular distribution fits for $\alpha$ scattering on ${}^{58}\mathrm{Ni}$ obtained using the velocity-dependent optical model (VDOM).

Figure 7

Our best angular distribution fits for $\alpha$ scattering on ${}^{208}\mathrm{Pb}$ obtained using the velocity-dependent optical model (VDOM).