Nuclear Structure Studies with Gamma-Ray Beams

¹ Lawrence Livermore National Laboratory, Physics Division, Livermore, California 94550, USA
² Los Alamos National Laboratory, Chemistry Division, Los Alamos, New Mexico 87545, USA
³ Duke University, Durham, North Carolina 27708, USA
⁴ Triangle Universities Nuclear Laboratory, Durham, North Carolina 27708, USA
⁵ North Carolina State University, Raleigh, North Carolina 27695, USA
⁶ UGC-DAE Consortium for Scientific Research, Kolkata Centre, Kolkata, India
⁷ McMaster University, Hamilton, ON, Canada
⁸ Institut för Theoretische Physik, Universitàt Giessen, Germany
⁹ Institute for Nuclear Research and Nuclear Energy, 1784 Sofia, Bulgaria

^a Corresponding author: tonchev2@llnl.gov

Published online: 28 May 2015

Abstract

In stable and weakly bound neutron-rich nuclei, a resonance-like concentration of dipole states has been observed for excitation energies below the neutron-separation energy. This clustering of strong dipole states has been named the Pygmy Dipole Resonance (PDR) in contrast to the Giant Dipole Resonance (GDR) that dominates the E1 response. Understanding the PDR is presently of great interest in nuclear structure and nuclear astrophysics. High-sensitivity studies of E1 and M1 transitions in closed-shell nuclei using monoenergetic and 100% linearly-polarized photon beams are presented.