Measurements of ${}^{152}\mathrm{Gd}(p,\gamma ){}^{153}\mathrm{Tb}$ and ${}^{152}\mathrm{Gd}(p,n){}^{152}\mathrm{Tb}$ reaction cross sections for the astrophysical $\gamma$ process

The total cross sections for the ${}^{152}\mathrm{Gd}\left(p,\gamma \right){}^{153}\mathrm{Tb}$ and ${}^{152}\mathrm{Gd}(p,{n)}^{152}\mathrm{Tb}$ reactions have been measured by the activation method at effective center-of-mass energies $3.47\le E_{\mathrm{c}}.\mathrm{m}{.}^{\mathrm{eff}}\le 7.94$ MeV and $4.96\le E_{\mathrm{c}}.\mathrm{m}{.}^{\mathrm{eff}}\le 7.94$ MeV, respectively. The targets were prepared by evaporation of 30.6% isotopically enriched ${}^{152}\mathrm{Gd}$ oxide on aluminum backing foils, and bombarded with proton beams provided by a cyclotron accelerator. The cross sections were deduced from the observed $\gamma$-ray activity, which was detected off-line by an HPGe detector in a low background environment. The results are presented and compared with predictions of statistical model calculations. This comparison supports a modified optical proton+${}^{152}\mathrm{Gd}$ potential suggested earlier.

Figure 1

A schematic diagram of the irradiation chamber mounted at the end of the beam line at the cyclotron accelerator of MTA Atomki.

Figure 2

The $\gamma$-ray spectrum recorded for a counting time of 3.64 h after 2.08 h of activation with a 7-MeV proton beam. The $\gamma$ transitions used in the measurements are indicated by arrows.

Figure 3

Experimental cross sections of ${}^{152}\mathrm{Gd}\left(p,\gamma \right){}^{153}\mathrm{Tb}$ and ${}^{152}\mathrm{Gd}(p,{n)}^{152}\mathrm{Tb}$ reactions.

Figure 4

Sensitivity of the astrophysical reaction rates for ${}^{152}\mathrm{Gd}\left(p,\gamma \right){}^{153}\mathrm{Tb}$ to a variation of total proton, neutron, and $\gamma$ widths as a function of plasma temperature $T$. The temperature range relevant for the nucleosynthesis of heavy $p$ nuclei is marked by the shaded area.

Figure 5

Sensitivity of the cross sections of ${}^{152}\mathrm{Gd}\left(p,\gamma \right){}^{153}\mathrm{Tb}$ to a variation of total proton, neutron, and $\gamma$ widths as function of center-of-mass energy $E_{\mathrm{c}}.\mathrm{m}.$.

Figure 6

Same as Fig. 5 but for ${}^{152}\mathrm{Gd}(p,{n)}^{152}\mathrm{Tb}$.

Figure 7

Experimental cross sections (exp) of ${}^{152}\mathrm{Gd}\left(p,\gamma \right){}^{153}\mathrm{Tb}$ as a function of effective center-of-mass energy $E_{\mathrm{c}}.\mathrm{m}{.}^{\mathrm{eff}}$, compared to statistical model calculations using different optical $p+{}^{152}\mathrm{Gd}$ potentials: the potentials by [71, 72] (Lej), by [73] (Lane consist.), and by [37, 38, 45] (mod Lej).

Figure 8

Same as Fig. 7 but for ${}^{152}\mathrm{Gd}(p,{n)}^{152}\mathrm{Tb}$.