Role of $p$-induced population of medium-mass $\left(A\sim 150\right)$ neutron-rich nuclei

Excitation functions were measured by stacked-foil activation technique for the ${}^{150}\mathrm{Nd}(p,xpyn)$ reaction using a 97.65% enriched ${}^{150}\mathrm{Nd}$ target. Measurement up to $\sim 50\%$ above barrier and down to 18% below the barrier was performed using a proton beam energy $\left(E_p\right)$ of 7–15 MeV from the VECC Cyclotron. The yield of suitable $\gamma$ rays emitted following the decay of relevant evaporation residues was determined using a 50% high-purity germanium (HPGe) detector. The $(p,n)$ cross section was found to follow the expected trend with a maximum value of 63.7(4.9) mb at $E_p\sim 8.6$ MeV. The $(p,2n)$ cross section gradually increased with $E_p$ and had a maximum contribution to the total reaction cross section after $E_p\sim 9.0$ MeV. The ${(p,p}^{\prime }n)$ reaction channel also showed a reasonable yield with a threshold of $E_p\sim 12.0$ MeV. The experimental data were corroborated with statistical model calculations using different codes, viz., cascade, alice/91, and empire3.1. All the calculations using a suitable set of global parameters could reproduce the excitation function fairly well in the present energy range.

Figure 1

The configuration of a typical stack is represented. The number, shape, and size of the targets, foils, and degraders were different in different stacks as detailed in the text. T1, T2, and T3 are the targets and Cu represents the monitor foil.

Figure 2

The total gamma spectrum taken with the 50% HPGe detector for the irradiated ${}^{150}\mathrm{Nd}$ target with 15 MeV proton beam. The photopeaks marked with *, **, ***, **** belong to the decay of ${}^{150}\mathrm{Pm},{}^{149}\mathrm{Pm},{}^{149}\mathrm{Nd}$, and the Al related or background $\gamma$ rays respectively.

Figure 3

The decay plots for the transitions characterizing the decay of different evaporation residues formed at a particular beam energy as described in the text.

Figure 4

The extracted efficiency of the 50% HPGe detector used in the experiment. The efficiency of the detector at distances of 7 cm and 15 cm from the detector is shown in the bottom and top panels respectively with black circles. The solid lines in the two figures represent the fitted curve.

Figure 5

Excitation function for ${}^{150}\text{Nd}(p,xnyp)$ reaction. Experimental data points for (a) ${}^{150}\mathrm{Pm}$, (b) ${}^{149}\mathrm{Pm}$, (c) ${}^{149}\mathrm{Nd}$, and (d) total CS are shown with open $\circ$. The calculated values of CS obtained from the work of O. Lebeda et al., are shown with $☆$. Theoretical CSs calculated from empire3.1, alice/91, and cascade are shown with dotted, solid, and dash-dotted lines respectively.

Figure 6

Individual CSs for different evaporation residues and total CS are plotted in logarithmic scale. Legends used are same as in Fig. 5.