Soft structures of γ-ray strength functions studied with the Oslo method

A.C. Larsen^1a, U. Agvaanluvsan^2,3, L.A. Bernstein⁴, A. Brger¹, R. Chankova⁵, S. Goriely⁶, M. Guttormsen¹, T. Lönnroth⁷, G.E. Mitchell⁵, H.T. Nyhus¹, A. Schiller⁸, S. Siem¹, N.U.H. Syed¹, H.K. Toft¹ and A. Voinov⁸

¹ Department of Physics, University of Oslo, N-0316 Oslo, Norway
² Stanford University, Palo Alto, California 94305 USA
³ MonAme Scientific Research Center Ulaanbaatar, Mongolia
⁴ Lawrence Livermore National Laboratory, Livermore, California 94551, USA
⁵ Department of Physics, North Carolina State University, Raleigh, North Carolina 27695, USA
⁶ Institut d’Astronomie et d’Astrophysique Université Libre de Bruxelles, CP 226, 1050 Brussels, Belgium
⁷ Department of Physics, Åbo Akademi, FIN-20500 Åbo, Finland
⁸ Department of Physics, Ohio University, Athens, OH 45701, USA

^a e-mail: a.c.larsen@fys.uio.no

Abstract

We present experimental γ-ray strength functions up to E_γ ∼ S_n measured at the Oslo Cyclotron Laboratory for several Sc, V, Mo, and Sn isotopes. For the lighter nuclei, an unexpected enhancement of the strength function at low γ-ray energies has been revealed. This enhancement could potentially have an impact on neutron-capture cross sections for unstable, neutron-rich nuclei. For the Sn isotopes, we observe increased strength around the neutron separation energy S_n.