Feeding of Rh and Ag isomers in fast-neutron-induced reactions

Abstract

Background: In (n, n ′ ) reactions on stable Ir and Au isotopes in the mass A = 190 region the experimentally established feeding of the isomers relative to the feeding of the corresponding ground states increases with increasing neutron energy up to the neutron energy where the (n, 2n) reaction channel opens up and then decreases.Purpose: In order to check for similar behavior in the mass A = 100 region the feeding of isomers and ground states in fast-neutron-induced reactions on stable isotopes in this mass region was studied. This is of especial interest for Rh which can be used as a radiochemical detector.Methods: Excited states were studied using the (n, n ′ γ), (n, 2nγ) and (n, 3nγ) reactions on 103 Rh and 109 Ag. A germanium-detector array for γ-ray detection and the broad-spectrum pulsed neutron source of the Los Alamos Neutron Science Center's Weapons Neutron Research facility were used for the measurement. The energy of the incident neutrons was determined using the time-of-flight technique.Results: Absolute partial γ-ray cross sections were measured for 57 transitions feeding isomers and ground states in 101,102,103 Rh and 107,108,109 Ag. The feeding of the isomers was found to be very similar in the corresponding reaction channels and it is compared to the feeding determined for the ground states. Conclusions:The opening of reaction channels at higher neutron energies removes angular momentum from the residual nucleus and reduces the population of the higher-spin isomers relative to the feeding of the lower-spin ground states. Similar behavior was observed in the mass A = 190 region in the feeding of higher-spin isomers, but the reverse behavior was observed in 176 Lu with a lower-spin isomer and a higher-spin ground state.PACS numbers: PACS number(s): 25.40.-h, 28.20.-v, 24.10.-i, 25.40.Fq * fotia@lanl.gov 2

Study of (n, 2n) reaction cross sections for 107Ag within the energy range of 9–22 MeV

“…Thus, the usefulness of the monoenergetic neutron source is only slightly impaired. The three-body breakup reaction 7 Li(p, n 3 He) 4 He takes place above 3.68 MeV, which contributes neutrons with primary neutron peak (n 0 ). The threshold for the reaction 7 Li(p, n) 7 Be is 7.06 MeV.…”

“…Hence, the neutroninduced reaction cross-sections data of Ag isotopes are important for nuclear applications. The (n, 2n) reactions of the two naturally occurring silver isotopes are potentially useful for the dosimetry of short pulses of d + T neutrons, the cross sections being fairly high and the half-lives of the induced activities reasonably short [3,4].…”

Advances in nuclear reaction calculations by incorporating information from nuclear mean-field theories

“…CoH 3 is extensively utilized in the nuclear data evaluation above the resonance region at LANL, as well as for the interpretation of experimental data at LANSCE (Los Alamos Neutron Science Center), e.g., the neutron capture measurements with the DANCE detector [9,13], and the γ -ray production measurements with the GEANIE detector [14,15].…”