Evidence for Pygmy and Giant Dipole Resonances in {sup 130}Sn and {sup 132}Sn

Journal Article · Fri Sep 23 00:00:00 EDT 2005 · Physical Review Letters

DOI:https://doi.org/10.1103/PhysRevLett.95.132501· OSTI ID:20696499

Adrich, P; Klimkiewicz, A ^[1]; Fallot, M; Boretzky, K; Aumann, T; Pramanik, U Datta; Emling, H; Geissel, H; Hellstroem, M; Jones, K L; Leifels, Y; Simon, H; Suemmerer, K ^[1]; Cortina-Gil, D ^[2]; Elze, Th W; Palit, R ^[3]; Kratz, J V; Nociforo, C ^[4]; Kulessa, R; Surowka, G ^[5]

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1. Gesellschaft fuer Schwerionenforschung (GSI), D-64291 Darmstadt (Germany)
2. Universidad de Santiago de Compostela, 15706, Santiago de Compostela (Spain)
3. Institut fuer Kernphysik, Johann Wolfgang Goethe-Universitaet, D-60486 Frankfurt (Germany)
4. Institut fuer Kernchemie, Johannes Gutenberg-Universitaet, D-55099 Mainz (Germany)
5. Instytut Fizyki, Uniwersytet Jagiellonski, PL-30-059 Cracow (Poland); and others

The dipole strength distribution above the one-neutron separation energy was measured in the unstable {sup 130}Sn and the double-magic {sup 132}Sn isotopes. The results were deduced from Coulomb dissociation of secondary Sn beams with energies around 500 MeV/nucleon, produced by in-flight fission of a primary {sup 238}U beam. In addition to the giant dipole resonance, a resonancelike structure ('pygmy resonance') is observed at a lower excitation energy around 10 MeV exhausting a few percent of the isovector E1 energy-weighted sum rule. The results are discussed in the context of a predicted new dipole mode of excess neutrons oscillating out of phase with the core nucleons.

• OSTI ID: 20696499
• Journal Information: Physical Review Letters, Vol. 95, Issue 13; Other Information: DOI: 10.1103/PhysRevLett.95.132501; (c) 2005 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 0031-9007
• Country of Publication: United States
• Language: English

Related Subjects

73 NUCLEAR PHYSICS AND RADIATION PHYSICS
DIPOLES
EXCITATION
FISSION
GIANT RESONANCE
ISOVECTORS
MEV RANGE 10-100
MEV RANGE 100-1000
NEUTRON SEPARATION ENERGY
NEUTRONS
SUM RULES
TIN 130
TIN 132
URANIUM 238 BEAMS