Stellar neutron capture cross sections of the Nd isotopes

The neutron capture cross sections of ${}^{142}$Nd, ${}^{143}$Nd, ${}^{144}$Nd, ${}^{145}$Nd, ${}^{146}$Nd, and ${}^{148}$Nd have been measured in the energy range from 3 to 225 keV at the Karlsruhe 3.75 MV Van de Graaff accelerator. Neutrons were produced via the ${}^7$Li$\mathrm{}(p,n)\mathrm{}$ ${}^7$Be reaction by bombarding metallic Li targets with a pulsed proton beam. Capture events were registered with the Karlsruhe 4$\pi$ Barium Fluoride Detector. The cross sections were determined relative to the gold standard. The experiment was difficult due to the small cross sections of the even isotopes at or near the magic neutron number $N$=82, and also since the isotopic enrichment of some samples was comparably low. The necessary corrections for capture of scattered neutrons and for isotopic impurities could be determined reliably thanks to the high efficiency and the spectroscopic quality of the BaF${}_2$ detector, resulting in a consistent set of $(n,\gamma )$ cross sections for the six stable neodymium isotopes involved in the $s$ process with typical uncertainties of 1.5–2 %. From these data, Maxwellian averaged cross sections were calculated between $kT=10\mathrm{}$ and 100 keV. The astrophysical implications of these results were investigated in an $s$-process analysis, which deals with the role of the $s$-only isotope ${}^{142}$Nd for the $N_s〈\sigma 〉$ systematics near the magic neutron number $N=82\mathrm{}$, the decomposition of the Nd abundances into the respective $r$-, $s$-, and $p$-process components, and the interpretation of isotopic anomalies in meteoritic material.