Neutron capture reactions near the $N=82$ shell-closure

Neutron capture cross sections have been calculated in nuclei near the $N=82$ neutron shell-closure. These nuclei are of astrophysical interest, participating in the $s$-process and the $p$-process. A semimicroscopic optical model has been used with the potential being obtained through folding the target density with the DDM3Y nucleon-nucleon interaction. Theoretical density values have been calculated using the relativistic mean-field approach. The calculated cross sections, as a function of neutron energy, agree reasonably well with experimental measurements. Maxwellian-averaged cross sections, important for astrophysical processes, have been calculated.

Figure 1

Charge density in several $N=82$ nuclei. Solid lines denote the model values using the parameters obtained from fitting the experimental data. Dashed lines indicate our results.

Figure 2

Differential angular distribution for elastic scattering of neutrons from ($\mathrm{a}){}^{140}\mathrm{Ce}$ at 1.5 MeV, (b) ${}^{140}\mathrm{Ce}$ at 2.0 MeV, (c) ${}^{140}\mathrm{Ce}$ at 2.5 MeV, (d) ${}^{140}\mathrm{Ce}$ at 3.0 MeV, (e) ${}^{141}\mathrm{Pr}$ at 0.878 MeV, (f) ${}^{141}\mathrm{Pr}$ at 1.2 MeV, (g) ${}^{142}\mathrm{Nd}$ at 2.5 MeV, and (h) ${}^{148}\mathrm{Sm}$ at 2.47 MeV. Solid lines denote theoretical data and discrete points represent experimental data.

Figure 3

Comparison of the results of the present calculation with experimental measurements for ${}^{133}\mathrm{Cs}, {}^{139}\mathrm{La}, {}^{140}\mathrm{Ce}$, and ${}^{141}\mathrm{Pr}$. The solid lines indicate the theoretical results. For convenience, cross-section values for ${}^{141}\mathrm{Pr}$ have been multiplied by a factor of 100.

Figure 4

Comparison of the results of the present calculation with experimental measurements for ${}^{135-138}\mathrm{Ba}$. The solid lines indicate the theoretical results. For convenience, cross-section values for ${}^{135,136}\mathrm{Ba}$ have been multiplied by a factor of 10.

Figure 5

Comparison of the results of the present calculation with experimental measurements for ${}^{142-146}\mathrm{Nd}$. The solid lines indicate the theoretical results. For convenience, cross-section values for ${}^{143,144}\mathrm{Nd}$ have been multiplied by a factor of 10.

Figure 6

Comparison of the results of the present calculation with experimental measurements for ${}^{144,147-149}\mathrm{Sm}$. The solid lines indicate the theoretical results. For convenience, cross-section values for ${}^{148,149}\mathrm{Sm}$ have been multiplied by a factor of 10.

Figure 7

The Neutron capture cross sections on the ${}^{144}\mathrm{Sm}$ target are shown with two different optical model potential calculations and plotted against experimental data. The solid line denotes the present formalism and the dotted line represents the JLM optical model potential.

Figure 8

The $s$-process path near the shell closure at $N=82$. Also shown are some of the $p$ nuclei. See text for more details.