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Title: Search for unbound Be 15 states in the 3 n + Be 12 channel

Abstract

Background: Be-15 is expected to have low-lying 3/2(+) and 5/2(+) states. A first search did not find the 3/2(+) [A. Spyrou et al., Phys. Rev. C 84, 044309 (2011)]; however, a resonance in Be-15 was populated in a second attempt and determined to be unbound with respect to Be-14 by 1.8(1) MeV with a tentative spin-parity assignment of 5/2(+) [J. Snyder et al., Phys. Rev. C 88, 031303(R) (2013)]. Purpose: Search for the predicted Be-15 3/2(+) state in the three-neutron decay channel. Method: A two-proton removal reaction from a 55 MeV/u C-17 beam was used to populate neutron-unbound states in Be-15. The two-, three-, and four-body decay energies of the Be-12+ neutron(s) detected in coincidence were reconstructed using invariant mass spectroscopy. Monte Carlo simulations were performed to extract the resonance and decay properties from the observed spectra. Results: The low-energy regions of the decay energy spectra can be described with the first excited unbound state of Be-14 (E-x = 1.54 MeV, E-r = 0.28 MeV). Including a state in Be-15 that decays through the first excited Be-14 state slightly improves the fit at higher energies though the cross section is small. Conclusions: A Be-15 component is not needed to describemore » the data. If the 3/2(+) state in Be-15 is populated, the decay by three-neutron emission through Be-14 is weak,« less

Authors:
 [1];  [1];  [1];  [1];  [1];  [2];  [3];  [4];  [1];  [1];  [1];  [5];  [1]
  1. Michigan State Univ., East Lansing, MI (United States)
  2. Hope College, Holland, MI (United States)
  3. Central Michigan Univ., Mount Pleasant, MI (United States)
  4. Augustana College, Rock Island, IL (United States)
  5. Rutgers Univ., Piscataway, NJ (United States)
Publication Date:
Research Org.:
Nuclear Science and Security Consortium, Berkeley, CA (United States)
Sponsoring Org.:
USDOE National Nuclear Security Administration (NNSA)
OSTI Identifier:
1454846
Grant/Contract Number:  
NA0000979
Resource Type:
Accepted Manuscript
Journal Name:
Physical Review. C, Nuclear Physics
Additional Journal Information:
Journal Volume: 91; Journal Issue: 1; Journal ID: ISSN 0556-2813
Publisher:
American Physical Society (APS)
Country of Publication:
United States
Language:
English
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS

Citation Formats

Kuchera, A. N., Spyrou, A., Smith, J. K., Baumann, T., Christian, G., DeYoung, P. A., Finck, J. E., Frank, N., Jones, M. D., Kohley, Z., Mosby, S., Peters, W. A., and Thoennessen, M. Search for unbound Be15 states in the 3n+Be12 channel. United States: N. p., 2015. Web. doi:10.1103/PhysRevC.91.017304.
Kuchera, A. N., Spyrou, A., Smith, J. K., Baumann, T., Christian, G., DeYoung, P. A., Finck, J. E., Frank, N., Jones, M. D., Kohley, Z., Mosby, S., Peters, W. A., & Thoennessen, M. Search for unbound Be15 states in the 3n+Be12 channel. United States. doi:10.1103/PhysRevC.91.017304.
Kuchera, A. N., Spyrou, A., Smith, J. K., Baumann, T., Christian, G., DeYoung, P. A., Finck, J. E., Frank, N., Jones, M. D., Kohley, Z., Mosby, S., Peters, W. A., and Thoennessen, M. Wed . "Search for unbound Be15 states in the 3n+Be12 channel". United States. doi:10.1103/PhysRevC.91.017304. https://www.osti.gov/servlets/purl/1454846.
@article{osti_1454846,
title = {Search for unbound Be15 states in the 3n+Be12 channel},
author = {Kuchera, A. N. and Spyrou, A. and Smith, J. K. and Baumann, T. and Christian, G. and DeYoung, P. A. and Finck, J. E. and Frank, N. and Jones, M. D. and Kohley, Z. and Mosby, S. and Peters, W. A. and Thoennessen, M.},
abstractNote = {Background: Be-15 is expected to have low-lying 3/2(+) and 5/2(+) states. A first search did not find the 3/2(+) [A. Spyrou et al., Phys. Rev. C 84, 044309 (2011)]; however, a resonance in Be-15 was populated in a second attempt and determined to be unbound with respect to Be-14 by 1.8(1) MeV with a tentative spin-parity assignment of 5/2(+) [J. Snyder et al., Phys. Rev. C 88, 031303(R) (2013)]. Purpose: Search for the predicted Be-15 3/2(+) state in the three-neutron decay channel. Method: A two-proton removal reaction from a 55 MeV/u C-17 beam was used to populate neutron-unbound states in Be-15. The two-, three-, and four-body decay energies of the Be-12+ neutron(s) detected in coincidence were reconstructed using invariant mass spectroscopy. Monte Carlo simulations were performed to extract the resonance and decay properties from the observed spectra. Results: The low-energy regions of the decay energy spectra can be described with the first excited unbound state of Be-14 (E-x = 1.54 MeV, E-r = 0.28 MeV). Including a state in Be-15 that decays through the first excited Be-14 state slightly improves the fit at higher energies though the cross section is small. Conclusions: A Be-15 component is not needed to describe the data. If the 3/2(+) state in Be-15 is populated, the decay by three-neutron emission through Be-14 is weak,},
doi = {10.1103/PhysRevC.91.017304},
journal = {Physical Review. C, Nuclear Physics},
number = 1,
volume = 91,
place = {United States},
year = {2015},
month = {1}
}

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Figures / Tables:

FIG. 1 FIG. 1: Select low-lying levels in beryllium isotopes from [10–12]. The dashed blue arrow represents the one-neutron decay from 15Be to 14Be [10] and the solid red arrows represent the suggested decay path in [8] searched for in this work. The red-shaded box represents the range of energies that weremore » simulated.« less

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    Figures/Tables have been extracted from DOE-funded journal article accepted manuscripts.