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

Larsen, A. C.; Guttormsen, M.; Blasi, N.; Bracco, A.; Camera, F.; Campo, L. Crespo; 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.; Tornyi, T. G.; Tveten, G. M.; Voinov, A. V.; Wiedeking, M.; Zeiser, F.

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

Date

2017-04-24

Authors

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.