74 Ge( n , γ ) cross section below 70 keV measured at n_TOF CERN

Abstract

Neutron capture reaction cross sections on ${}^{74}$ Ge are of importance to determine ${}^{74}$ Ge production during the astrophysical slow neutron capture process. We present new resonance data on ${}^{74}$ Ge( $n,\gamma$ ) reactions below 70 keV neutron energy. We calculate Maxwellian averaged cross sections, combining our data below 70 keV with evaluated cross sections at higher neutron energies. Our stellar cross sections are in agreement with a previous activation measurement performed at Forschungszentrum Karlsruhe by Marganiec et al., once their data has been re-normalised to account for an update in the reference cross section used in that experiment.

Fig. 1

Weighted count spectra from 1 eV to 100 keV neutron energy obtained at n_TOF for the ${}^{74}$Ge sample, the empty sample holder, and without neutron beam. The resonances below 1 keV come from isotopic impurities, mainly ${}^{73}$Ge

Fig. 2

n_TOF data and SAMMY fits for resonances at 2858 and 3051 eV compared to the ENDF/B-VIII evaluation, which is based on a measurement by Maletski et al. [7]

Fig. 3

n_TOF data and SAMMY fits for resonances from about 12 to 15 keV, where most resonances are observed for the first time

Fig. 4

Ratio of abundances for Ge (circles), As (star) , Se (triangles) and Br (squares) isotopes produced after carbon shell burning in a 15 solar mass star with metallicity $Z=$0.006, using ${}^{74}$Ge MACS of this work, compared to MACS from Marganiec et al. [9]. The lines connect isotopes belonging to the same element