Evidence for the dipole nature of the low-energy γ enhancement in 56Fe

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

doi:10.1103/PhysRevLett.111.242504

Evidence for the dipole nature of the low-energy γ enhancement in 56Fe

Phys Rev Lett. 2013 Dec 13;111(24):242504. doi: 10.1103/PhysRevLett.111.242504. Epub 2013 Dec 11.

Authors

A C Larsen¹, N Blasi², A Bracco³, F Camera³, T K Eriksen¹, A Görgen¹, M Guttormsen¹, T W Hagen¹, S Leoni³, B Million², H T Nyhus¹, T Renstrøm¹, S J Rose¹, I E Ruud¹, S Siem¹, T Tornyi⁴, G M Tveten¹, A V Voinov⁵, M Wiedeking⁶

Affiliations

¹ Department of Physics, University of Oslo, N-0316 Oslo, Norway.
² INFN, Sezione di Milano, I-20133 Milano, Italy.
³ INFN, Sezione di Milano, I-20133 Milano, Italy and Dipartimento di Fisica, University of Milano, I-20122 Milano, Italy.
⁴ Department of Physics, University of Oslo, N-0316 Oslo, Norway and Institute of Nuclear Research, MTA ATOMKI, H-4026 Debrecen, Hungary.
⁵ Department of Physics and Astronomy, Ohio University, Athens, Ohio 45701, USA.
⁶ iThemba LABS, Post Office Box 722, 7129 Somerset West, South Africa.

PMID: 24483649
DOI: 10.1103/PhysRevLett.111.242504

Abstract

The γ-ray strength function of 56Fe has been measured from proton-γ coincidences for excitation energies up to ≈11 MeV. The low-energy enhancement in the γ-ray strength function, which was first discovered in the (3He,αγ)56Fe reaction, is confirmed with the (p,p'γ)56Fe experiment reported here. Angular distributions of the γ rays give for the first time evidence that the enhancement is dominated by dipole transitions.