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Title: Isovector excitations in 100Nb and their decays by neutron emission studied via the Mo 100 ( t , He 3 + n ) reaction at 115 MeV/u

Here, spin–isospin excitations in 100Nb were studied via the charge-exchange reaction at 115 MeV/u with the goal to constrain theoretical models used to describe the isovector spin response of nuclei. The experiment was performed with a secondary beam of tritons, and 3He particles were analyzed in the S800 magnetic spectrometer. Decay by neutron emission from excited states in 100Nb was observed by using plastic and liquid scintillator arrays. Differential cross sections were analyzed and monopole excitations were revealed by using a multipole decomposition analysis. The Gamow–Teller transition strength observed at low excitation energies, which is important for estimating the electron-capture rate in astrophysical scenarios, was strongly fragmented and reduced compared to single-particle and spherical mean-field models. The consideration of deformation in the theoretical estimates was found to be important to better describe the fragmentation and strengths. A strong excitation of the isovector spin giant monopole resonance was observed, and well reproduced by the mean-field models. Its presence makes the extraction of Gamow–Teller strengths at high excitation energies difficult. The branches for statistical and direct decay by neutron emission were identified in the spectra. The upper limit for the branching ratio by direct decay (integrated over all observed excitations) was determinedmore » to be 20 ± 6%. Even though the statistical uncertainties in the neutron-coincident data were too large to perform detailed studies of the decay by neutron emission from individual states and resonances, the experiment demonstrates the feasibility of the method.« less
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  1. Michigan State Univ., East Lansing, MI (United States)
  2. Univ. of Tennessee, Knoxville, TN (United States)
  3. Univ. of Groningen, Groningen (Netherlands)
  4. Western Michigan Univ., Kalamazoo MI (United States); Michigan State Univ., East Lansing, MI (United States)
  5. Yale Univ., New Haven, CT (United States)
  6. Central Michigan Univ., Mount Pleasant, MI (United States); Michigan State Univ., East Lansing, MI (United States)
  7. Oak Ridge Associated Univ., Oak Ridge, TN (United States); Univ. of Tennessee, Knoxville, TN (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Publication Date:
Grant/Contract Number:
NA0003180; FG02-91ER40608
Published Article
Journal Name:
Physics Letters. Section B
Additional Journal Information:
Journal Volume: 769; Journal Issue: C; Journal ID: ISSN 0370-2693
Research Org:
The Regents of the Univ. of California, Berkeley, CA (United States). Nuclear Science and Security Consortium
Sponsoring Org:
USDOE National Nuclear Security Administration (NNSA), Office of Defense Nuclear Nonproliferation (NA-20)
Country of Publication:
United States
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; Spin–isospin excitations; Neutron decay; Charge-exchange reaction; Missing mass spectroscopy
OSTI Identifier:
Alternate Identifier(s):
OSTI ID: 1405175