Spectral structure of the pygmy dipole resonance

Phys Rev Lett. 2010 Feb 19;104(7):072501. doi: 10.1103/PhysRevLett.104.072501. Epub 2010 Feb 18.

Abstract

High-sensitivity studies of E1 and M1 transitions observed in the reaction 138Ba(gamma,gamma{'}) at energies below the one-neutron separation energy have been performed using the nearly monoenergetic and 100% linearly polarized photon beams of the HIgammaS facility. The electric dipole character of the so-called "pygmy" dipole resonance was experimentally verified for excitations from 4.0 to 8.6 MeV. The fine structure of the M1 "spin-flip" mode was observed for the first time in N=82 nuclei.