Elastic scattering of ${}^6\mathrm{Li}$ on ${}^{64}\mathrm{Zn}$ at near-barrier energies

Elastic-scattering angular distributions for the ${}^6\mathrm{Li}+{}^{64}\mathrm{Zn}$ system were measured at eight beam energies from below to above the Coulomb barrier, $12.0⩽E_{\mathrm{lab}}⩽22.0$ MeV. The experimental data were analyzed within the optical model to study the energy dependence of the interaction potential and to obtain total reaction cross sections. The results obtained using several optical model potentials show similar behavior. The energy dependence of the strengths of the real and imaginary potentials suggests the presence of the breakup threshold anomaly. It is shown that the extracted energy dependence of the interaction potential at sub-barrier energies is very sensitive to possible experimental errors.

Figure 1

Ratio of the elastic-scattering to Rutherford-scattering cross sections for the ${}^6\mathrm{Li}+{}^{64}\mathrm{Zn}$ system at the beam energy of 12 MeV measured with the detectors mounted to the left (solid circles) and right (solid squares) of the beam direction. The cross sections were determined (a) using the mean values of the solid-angle ratios (normalization A) and (b) measuring the solid-angle ratios for each position of the telescopes (normalization C). The lines represent the results of the fit using the double-folding potential DF1 (see Sec. 3).

Figure 2

Elastic-scattering angular distributions for the ${}^6\mathrm{Li}+{}^{64}\mathrm{Zn}$ system at the beam energy of 12 MeV obtained by averaging the “beam left” and “beam right” data. The cross sections were determined using the mean values of the solid-angle ratios (normalization A, solid squares) or measuring the solid-angle ratios for each position of the telescopes (normalization C, solid circles). The lines represent the results of the fit using the double-folding potential DF1 (see Sec. 3).

Figure 3

Elastic-scattering angular distributions for the ${}^6\mathrm{Li}+{}^{64}\mathrm{Zn}$ system. The different symbols represent the results obtained in the three different experiments: first experiment (solid triangles), second experiment (solid squares), and third experiment (solid circles). The lines represent the results of the fit with the double-folding potential DF1 (see Sec. 3).

Figure 4

Total reaction cross sections derived from the elastic-scattering data using the optical model potential DF1: solid triangles (first experiment), solid squares (second experiment), and solid circles (third experiment). The solid stars represent the data of Ref. [20]. The arrow indicates the position of the calculated Coulomb barrier (see text for details).

Figure 5

Energy dependence of the normalization factors $N_R$ and $N_I$ of the real and imaginary parts of the potential DF1, respectively, obtained from the fit to the experimental data: first experiment (solid triangles), second experiment (solid squares), and third experiment (solid circles). The arrow indicates the position of the calculated Coulomb barrier.

Figure 6

Energy dependence of the normalization factors $N_R$ and $N_I$ of the real and imaginary parts of the potential DF1 obtained from the fit to the experimental data with normalization AAA (normalization A for all three experiments): first experiment (solid triangles), second experiment (solid squares), and third experiment (solid circles). The arrow indicates the position of the calculated Coulomb barrier.

Figure 7

Energy dependence of the normalization factors of the real and imaginary parts ($N_R$ and $N_I$, respectively) of the potentials DF1 (open symbols) and DF2 (solid symbols): triangles (first experiment), squares (second experiment), and circles (third experiment). The arrow indicates the position of the calculated Coulomb barrier.

Figure 8

Energy dependence of the normalization factor $N_R$ of the double-folding real part and the depth $W_0$ of the Woods-Saxon imaginary part of the potentials DF1WS (open symbols) and DF2WS (solid symbols): triangles (first experiment), squares (second experiment), and circles (third experiment). The differences between the $W_0$ values for the two potentials are smaller than the symbol sizes The arrow indicates the position of the calculated Coulomb barrier.