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

A. C. Larsen; M. Guttormsen; N. Blasi; A. Bracco; F. Camera; L. Crespo Campo; T. K. Eriksen; A. Görgen; T. W. Hagen; V. W. Ingeberg; B. V. Kheswa; S. Leoni; J. E. Midtbø; B. Million; H. T. Nyhus; T. Renstrøm; S. J. Rose; I. E. Ruud; S. Siem; T. G. Tornyi; G. M. Tveten; A. V. Voinov; M. Wiedeking; F. Zeiser

doi:10.1088/1361-6471/aa644a

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

A. C. Larsen, M. Guttormsen, N. Blasi, A. Bracco, F. Camera, L. Crespo Campo, T. K. Eriksen, A. Görgen, T. W. Hagen, V. W. Ingeberg, B. V. Kheswa, S. Leoni, J. E. Midtbø, B. Million, H. T. Nyhus, T. Renstrøm, S. J. Rose, I. E. Ruud, S. Siem, T. G. TornyiG. M. Tveten, A. V. Voinov, M. Wiedeking, F. Zeiser

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Abstract

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, in support of the generalized Brink-Axel hypothesis.

Original language	English
Article number	064005
Journal	Journal of Physics G: Nuclear and Particle Physics
Volume	44
Issue number	6
DOIs	https://doi.org/10.1088/1361-6471/aa644a
Publication status	Published - 24 Apr 2017

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Larsen, A. C., Guttormsen, M., Blasi, N., Bracco, A., Camera, F., Campo, L. C., Eriksen, T. K., Görgen, A., Hagen, T. W., Ingeberg, V. W., Kheswa, B. V., Leoni, S., Midtbø, J. E., Million, B., Nyhus, H. T., Renstrøm, T., Rose, S. J., Ruud, I. E., Siem, S., ... Zeiser, F. (2017). Low-energy enhancement and fluctuations of γ-ray strength functions in ^56,57Fe: Test of the Brink-Axel hypothesis. Journal of Physics G: Nuclear and Particle Physics, 44(6), Article 064005. https://doi.org/10.1088/1361-6471/aa644a

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title = "Low-energy enhancement and fluctuations of γ-ray strength functions in 56,57Fe: Test of the Brink-Axel hypothesis",

abstract = "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, in support of the generalized Brink-Axel hypothesis.",

keywords = "Brink hypothesis, angular distributions, iron, level density, γ-strength function",

author = "Larsen, {A. C.} and M. Guttormsen and N. Blasi and A. Bracco and F. Camera and Campo, {L. Crespo} and Eriksen, {T. K.} and A. G{\"o}rgen and Hagen, {T. W.} and Ingeberg, {V. W.} and Kheswa, {B. V.} and S. Leoni and Midtb{\o}, {J. E.} and B. Million and Nyhus, {H. T.} and T. Renstr{\o}m and Rose, {S. J.} and Ruud, {I. E.} and S. Siem and Tornyi, {T. G.} and Tveten, {G. M.} and Voinov, {A. V.} and M. Wiedeking and F. Zeiser",

note = "Publisher Copyright: {\textcopyright} 2017 IOP Publishing Ltd.",

year = "2017",

month = apr,

day = "24",

doi = "10.1088/1361-6471/aa644a",

language = "English",

volume = "44",

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Larsen, AC, Guttormsen, M, Blasi, N, Bracco, A, Camera, F, Campo, LC, Eriksen, TK, Görgen, A, Hagen, TW, Ingeberg, VW, Kheswa, BV, Leoni, S, Midtbø, JE, Million, B, Nyhus, HT, Renstrøm, T, Rose, SJ, Ruud, IE, Siem, S, Tornyi, TG, Tveten, GM, Voinov, AV, Wiedeking, M & Zeiser, F 2017, 'Low-energy enhancement and fluctuations of γ-ray strength functions in ^56,57Fe: Test of the Brink-Axel hypothesis', Journal of Physics G: Nuclear and Particle Physics, vol. 44, no. 6, 064005. https://doi.org/10.1088/1361-6471/aa644a

TY - JOUR

T1 - Low-energy enhancement and fluctuations of γ-ray strength functions in 56,57Fe

T2 - Test of the Brink-Axel hypothesis

AU - Larsen, A. C.

AU - Guttormsen, M.

AU - Blasi, N.

AU - Bracco, A.

AU - Camera, F.

AU - Campo, L. Crespo

AU - Eriksen, T. K.

AU - Görgen, A.

AU - Hagen, T. W.

AU - Ingeberg, V. W.

AU - Kheswa, B. V.

AU - Leoni, S.

AU - Midtbø, J. E.

AU - Million, B.

AU - Nyhus, H. T.

AU - Renstrøm, T.

AU - Rose, S. J.

AU - Ruud, I. E.

AU - Siem, S.

AU - Tornyi, T. G.

AU - Tveten, G. M.

AU - Voinov, A. V.

AU - Wiedeking, M.

AU - Zeiser, F.

PY - 2017/4/24

Y1 - 2017/4/24

N2 - 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, in support of the generalized Brink-Axel hypothesis.

AB - 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, in support of the generalized Brink-Axel hypothesis.

KW - Brink hypothesis

KW - angular distributions

KW - iron

KW - level density

KW - γ-strength function

UR - http://www.scopus.com/inward/record.url?scp=85019888774&partnerID=8YFLogxK

U2 - 10.1088/1361-6471/aa644a

DO - 10.1088/1361-6471/aa644a

M3 - Article

SN - 0954-3899

VL - 44

JO - Journal of Physics G: Nuclear and Particle Physics

JF - Journal of Physics G: Nuclear and Particle Physics

IS - 6

M1 - 064005

ER -

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

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