Indirect determination of neutron-capture cross sections for Sm isotopes

Neutron-capture cross sections in the energy range of 0.01–10 MeV for ${}^{146,148,150,152}\mathrm{Sm}$ nuclei were calculated using the $\gamma$-ray strength and level density functions extracted from the Oslo-type experiments. The uncertainties in the cross-section values were determined using a Monte Carlo method. For the ${}^{148,150,152}\mathrm{Sm}$ isotopes, the calculated cross sections are in a good agreement with the existing experimental data and for the ${}^{146}\mathrm{Sm}$ nucleus, an experimental $(n,\gamma )$ cross section is reported for the first time. The results are compared with the ENDF, EAF, and TENDL evaluations. Maxwellian-averaged cross sections were also calculated using the same input $\gamma \mathrm{SF}$ and LD functions.

Figure 1

$\gamma \mathrm{SF}$ compared with experimental data from Refs. [11, 12]. Red lines indicate the $E1$ components; blue, the $M1$; black, total $\gamma \mathrm{SF}$. The solid red line is the EGLo strength used in this work; red dashed line, the GLo available in talys 1.9. The black dotted lines indicate the uncertainty in the $\gamma \mathrm{SF}$ based on the uncertainties of the parameters in Table 1.

Figure 2

A sample distribution of the cross section values around the centroid for 10 MeV neutrons in ${}^{152}\mathrm{Sm}$ ($n,\gamma ){}^{153}\mathrm{Sm}$ reaction. Red curve is a Gaussian shape fitted to the distribution in order to determine the $\sigma$ value.

Figure 3

Neutron capture cross sections obtained in this work. The solid black line is the cross section obtained in this work with a $\gamma \mathrm{SF}$ containing $E1$ EGLo, $M1$ spin-flip, scissors mode (if present) and up-bend as defined in Table 1. The red lines indicate ($n,\gamma$) cross sections obtained for: the EGLo $E1$ function with the talys default for $M1$ component (dashed), EGLo with $M1$ as defined in Table 1 (dotted), and EGLo with spin-flip and scissors mode (dot-dashed). The gray shaded area indicates the range of talys predictions with all possible combinations of $\gamma \mathrm{SF}$ and LD models, the blue shaded area denotes the $1\sigma$ uncertainty obtained from the Monte Carlo analysis. The experimental data were extracted from the EXFOR database [14] and the evaluation data from ENDF [15].