|
|
Guerrero, C., Tessler, M., Paul, M., Lerendegui-Marco, J., Heinitz, S., Maugeri, E. A., et al. (2019). The s-process in the Nd-Pm-Sm region: Neutron activation of Pm-147. Phys. Lett. B, 797, 134809–6pp.
Abstract: The Nd-Pm-Sm branching is of interest for the study of the s-process, related to the production of heavy elements in stars. As Sm-148 and Sm-150 are s-only isotopes, the understanding of the branching allows constraining the s-process neutron density. In this context the key physics input needed is the cross section of the three unstable nuclides in the region: Nd-147 (10.98 d half-life), Pm-147 (2.62 yr) and Pm-148 (5.37 d). This paper reports on the activation measurement of Pm-147, the longest-lived of the three nuclides. The cross section measurement has been carried out by activation at the SARAF LiLiT facility using a 56(2) μg target. Compared to the single previous measurement of Pm-147, the measurement presented herein benefits from a target 2000 times more massive. The resulting Maxwellian Averaged Cross Section (MACS) to the ground and metastable states in Pm-148 are 469(50) mb and 357(27) mb. These values are 41% higher (to the ground state) and 15% lower (to the metastable state) than the values reported so far, leading however to a total cross section of 826(107) mb consistent within uncertainties with the previous result and hence leaving unchanged the previous calculation of the s-process neutron density.
|
|
|
|
Lerendegui-Marco, J. et al, Balibrea-Correa, J., Babiano-Suarez, V., Domingo-Pardo, C., de la Fuente-Rosales, G., Gameiro, B., et al. (2026). Direct Experiments of Neutron Capture on Stable and Unstable Isotopes for Stellar Nucleosynthesis Studies. Galaxies, 14(3), 59–26pp.
Abstract: Neutron capture reactions provide essential nuclear physics input for modeling the synthesis of heavy elements in stars. The growing precision of stellar spectroscopy and isotopic measurements in presolar SiC grains now demands cross sections with improved accuracy over the full energy range, and access to unstable nuclei relevant to slow (s-) process branchings and the intermediate (i-) process. This article reviews recent progress in direct neutron capture measurements, focusing on time-of-flight (TOF) experiments at CERN n_TOF and complementary activation techniques. Substantial advances have been achieved for stable s-only and bottleneck isotopes, significantly improving constraints on s-process models. In parallel, the combination of high instantaneous neutron fluxes and advanced detector systems has facilitated first-time neutron capture measurements on several radioactive branching-point nuclei. Feasibility studies, however, reveal current limitations related to sample availability, background conditions, and restricted energy coverage. In this context, the complementarity between TOF and activation emerges as a central strategy. Future developments, including high-flux facilities and novel inverse kinematics experiments in ion storage rings, are expected to extend the boundaries of neutron capture measurements, overcoming current limitations and helping unlock new frontiers in our understanding of stellar nucleosynthesis.
|
|
|
|
n_TOF Collaboration(Spelta, M. et al), Balibrea-Correa, J., Domingo-Pardo, C., Ladarescu, I., Lerendegui-Marco, J., & Tarifeño-Saldivia, A. (2026). First Results of the 64Ni(n,γ) Cross Section Measurement at n_TOF. Galaxies, 14(2), 29–8pp.
Abstract: The neutron capture cross section of 64Ni is an important parameter in nuclear astrophysics that is needed to accurately simulate stellar nucleosynthesis and validate stellar models. 64Ni is among the seeds of the s-process and its capture cross section has been found to have an important effect on the predicted abundances of many nuclei synthesized in Asymptotic Giant Branch (AGB) and massive stars. Despite its relevance, the measurements of the 64Ni(n,gamma) available in the literature are scarce and discrepant. For this reason, a new accurate time-of-flight measurement has been performed at the n_TOF facility at CERN, taking advantage of its high instantaneous neutron flux, and using a highly enriched 64Ni sample. The first preliminary results show important discrepancies with respect to the cross sections recommended in the most recent releases of the evaluated nuclear data libraries. In particular, a large resonance reported at 9.52 keV is not observed. As a consequence, a significant reduction in the Maxwellian-Averaged Cross Section (MACS) obtained from evaluated data libraries in the 5-25 keV thermal energy region is expected.
|
|
