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Title: Low-energy enhancement and fluctuations of γ -ray strength functions in 56,57 Fe: test of the Brink–Axel hypothesis

Nuclear level densities and γ-ray strength functions of 56,57Fe have been extracted from proton-γ coincidences. A low-energy enhancement in the γ-ray strength functions up to a factor of 30 over common theoretical E1 models is confirmed. Angular distributions of the low-energy enhancement in 57Fe indicate its dipole nature, in agreement with findings for 56Fe. The high statistics and the excellent energy resolution of the large-volume LaBr 3(Ce) detectors allowed for a thorough analysis of γ strength as function of excitation energy. Taking into account the presence of strong Porter–Thomas fluctuations, there is no indication of any significant excitation energy dependence in the γ-ray strength function, which is in support of the generalized Brink–Axel hypothesis.
Authors:
 [1] ;  [1] ;  [2] ;  [3] ;  [3] ;  [1] ;  [4] ;  [1] ;  [1] ;  [1] ;  [1] ;  [3] ;  [1] ;  [2] ;  [1] ;  [1] ;  [1] ;  [1] ;  [1] ;  [1] more »;  [1] ;  [5] ;  [6] ;  [1] « less
  1. Univ. of Oslo (Norway). Dept. of Physics
  2. National Inst. of Nuclear Physics (INFN), Milan (Italy)
  3. National Inst. of Nuclear Physics (INFN), Milan (Italy); Univ. of Milan (Italy). Dept. of Physics
  4. Univ. of Oslo (Norway). Dept. of Physics; Australian National Univ., Canberra, ACT (Australia). Dept. of Nuclear Physics
  5. Ohio Univ., Athens, OH (United States). Dept. of Physics and Astronomy
  6. iThemba LABS, Somerset West (South Africa)
Publication Date:
Grant/Contract Number:
NA0002905; 205528; 637686; 210007; 222287; 92789
Type:
Accepted Manuscript
Journal Name:
Journal of Physics. G, Nuclear and Particle Physics
Additional Journal Information:
Journal Volume: 44; Journal Issue: 6; Journal ID: ISSN 0954-3899
Publisher:
IOP Publishing
Research Org:
Ohio Univ., Athens, OH (United States)
Sponsoring Org:
USDOE National Nuclear Security Administration (NNSA); Univ. of Oslo (Norway); Research Council of Norway (NFR); European Research Council (ERC); National Research Foundation (NRF) (South Africa)
Country of Publication:
United States
Language:
English
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS; Gamma strength function; level density; angular distributions; Brink hypothesis; iron
OSTI Identifier:
1432356

Larsen, A. C., Guttormsen, M., Blasi, N., Bracco, A., Camera, F., Campo, L. Crespo, Eriksen, T. K., Gorgen, A., Hagen, T. W., Ingeberg, V. W., Kheswa, B. V., Leoni, S., Midtbo, J. E., Million, B., Nyhus, H. T., Renstrom, T., Rose, S. J., Ruud, I. E., Siem, S., Tornyi, T. G., Tveten, G. M., Voinov, A. V., Wiedeking, M., and Zeiser, F.. Low-energy enhancement and fluctuations of γ -ray strength functions in 56,57 Fe: test of the Brink–Axel hypothesis. United States: N. p., Web. doi:10.1088/1361-6471/aa644a.
Larsen, A. C., Guttormsen, M., Blasi, N., Bracco, A., Camera, F., Campo, L. Crespo, Eriksen, T. K., Gorgen, A., Hagen, T. W., Ingeberg, V. W., Kheswa, B. V., Leoni, S., Midtbo, J. E., Million, B., Nyhus, H. T., Renstrom, T., Rose, S. J., Ruud, I. E., Siem, S., Tornyi, T. G., Tveten, G. M., Voinov, A. V., Wiedeking, M., & Zeiser, F.. Low-energy enhancement and fluctuations of γ -ray strength functions in 56,57 Fe: test of the Brink–Axel hypothesis. United States. doi:10.1088/1361-6471/aa644a.
Larsen, A. C., Guttormsen, M., Blasi, N., Bracco, A., Camera, F., Campo, L. Crespo, Eriksen, T. K., Gorgen, A., Hagen, T. W., Ingeberg, V. W., Kheswa, B. V., Leoni, S., Midtbo, J. E., Million, B., Nyhus, H. T., Renstrom, T., Rose, S. J., Ruud, I. E., Siem, S., Tornyi, T. G., Tveten, G. M., Voinov, A. V., Wiedeking, M., and Zeiser, F.. 2017. "Low-energy enhancement and fluctuations of γ -ray strength functions in 56,57 Fe: test of the Brink–Axel hypothesis". United States. doi:10.1088/1361-6471/aa644a. https://www.osti.gov/servlets/purl/1432356.
@article{osti_1432356,
title = {Low-energy enhancement and fluctuations of γ -ray strength functions in 56,57 Fe: test of the Brink–Axel hypothesis},
author = {Larsen, A. C. and Guttormsen, M. and Blasi, N. and Bracco, A. and Camera, F. and Campo, L. Crespo and Eriksen, T. K. and Gorgen, A. and Hagen, T. W. and Ingeberg, V. W. and Kheswa, B. V. and Leoni, S. and Midtbo, J. E. and Million, B. and Nyhus, H. T. and Renstrom, T. and Rose, S. J. and Ruud, I. E. and Siem, S. and Tornyi, T. G. and Tveten, G. M. and Voinov, A. V. and Wiedeking, M. and Zeiser, F.},
abstractNote = {Nuclear level densities and γ-ray strength functions of 56,57Fe have been extracted from proton-γ coincidences. A low-energy enhancement in the γ-ray strength functions up to a factor of 30 over common theoretical E1 models is confirmed. Angular distributions of the low-energy enhancement in 57Fe indicate its dipole nature, in agreement with findings for 56Fe. The high statistics and the excellent energy resolution of the large-volume LaBr3(Ce) detectors allowed for a thorough analysis of γ strength as function of excitation energy. Taking into account the presence of strong Porter–Thomas fluctuations, there is no indication of any significant excitation energy dependence in the γ-ray strength function, which is in support of the generalized Brink–Axel hypothesis.},
doi = {10.1088/1361-6471/aa644a},
journal = {Journal of Physics. G, Nuclear and Particle Physics},
number = 6,
volume = 44,
place = {United States},
year = {2017},
month = {4}
}