Photoneutron cross sections for neodymium isotopes: Toward a unified understanding of $(\gamma ,n)$ and $(n,\gamma )$ reactions in the rare earth region

Photoneutron cross sections were measured for five stable Nd isotopes, ${}^{143,144,145,146,148}\mathrm{Nd}$, near neutron threshold with highly monochromatic laser-Compton scattering $\gamma$ rays. The photoneutron data were compared with the calculations performed with the talys reaction code with inputs of the Skyrme Hartree-Fock-Bogoliubov (HFB) plus quasi-particle random phase approximation (QRPA) model and the axially symmetric deformed Gogny HFB plus QRPA model of $E1$ $\gamma$-ray strength. Using the $\gamma$-ray strength function constrained by the present photoneutron data, a thorough analysis of the reverse $(n,\gamma )$ cross sections is made. Radiative neutron capture cross sections for an s-process branching-point nucleus in the rare earth region, ${}^{147}\mathrm{Nd}$ with the half-life 10.98 d, are deduced with the $\gamma$-ray strength function method. The impact of the newly evaluated ${}^{147}\text{Nd}{(n,\gamma )}^{148}\text{Nd}$ cross section on s-process nucleosynthesis is discussed.

Figure 1

The chart of nuclei depicting our systematic analysis of $(\gamma ,n)$ and $(n,\gamma )$ cross sections for Nd isotopes in the context of the $\gamma$-ray strength function method. Photoneutron cross sections measured in the present experiment are shown by left-pointing arrows. Radiative neutron capture cross sections discussed in the present systematic analysis are shown by right-pointing arrows. Photoneutron cross sections for the radioactive nucleus ${}^{147}\mathrm{Nd}$ are deduced with the $\gamma$-ray strength function method.

Figure 2

Comparison between the present photoneutron emission cross sections and previously measured ones [26] for ${}^{143\text{–}146,148}\mathrm{Nd}$. Also included are the predictions from Skyrme HFB + QRPA (based on the BSk7 interaction) [32] and axially deformed Gogny HFB + QRPA models (based on the D1M interaction) [34].

Figure 3

Comparison between the measured radiative neutron capture cross sections [40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50] with talys calculations making use of the D1M + QRPA $E1$ strength (solid line). The hashed area corresponds to uncertainties related to the NLD model and their normalization on experimental s-wave spacings at the neutron binding energy.

Figure 4

Prediction of the ${}^{147}\mathrm{Nd}\left(n,\gamma \right){}^{148}\mathrm{Nd}$ cross section. The dotted, dashed, and dash-dotted curves correspond to the JENDL-4.0 [54], ENDF/B-VII.1 [52], and ROSFOND-2010 [53] evaluations.

Figure 5

Comparison between our newly determined ${}^{147}\mathrm{Nd}\left(n,\gamma \right){}^{148}\mathrm{Nd}$ MACS with the values recommended in Ref. [55].

Figure 6

Final surface abundances $X$ for a $3M_{\odot }$ AGB model star of metallicity $Z=0.0001$ with respect to the solar values $X_{\odot }$ for all s-only nuclei and ${}^{148}\mathrm{Nd}$ as a function of the mass number $A$. The circles (including error bars) are obtained with the present ${}^{147}\mathrm{Nd}\left(n,\gamma \right){}^{148}\mathrm{Nd}$ MACS and the diamonds with the values given in Ref. [55]. The insert shows an enlargement of the $140\le A\le 160$ region.