Spectral structure of the pygmy dipole resonance.

Duke University, Durham, North Carolina 27708-0308, USA.
Physical Review Letters (Impact Factor: 7.73). 02/2010; 104(7):072501. DOI: 10.1103/PHYSREVLETT.104.072501
Source: PubMed

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.

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