Study of the Pygmy Dipole Resonance in {sup 124}Sn by means of the ({alpha},{alpha}'{gamma}) reaction

Journal Article · Wed Jan 28 00:00:00 EST 2009 · AIP Conference Proceedings

DOI:https://doi.org/10.1063/1.3087045· OSTI ID:21255440

Endres, J; Zilges, A ^[1]; Pietralla, N; Savran, D; Sonnabend, K ^[2]; Harakeh, M N; Stoica, V; Woertche, H ^[3]; Butler, P; Herzberg, R D; Scheck, M ^[4]; Kruecken, R ^[5]; Popescu, L ^[6]; Harissopulos, S; Lagoyannis, A ^[7]

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1. Institut fuer Kernphysik, Universitaet zu Koeln (Germany)
2. Institut fuer Kernphysik, TU Darmstadt (Germany)
3. Kernfysisch Versneller Instituut, University of Groningen (Netherlands)
4. Department of Physics, University of Liverpool (United Kingdom)
5. Physik-Department E12, TU Muenchen (Germany)
6. SCK-CEN, Mol (Belgium)
7. I.N.P. NCSR Demokritos, Athens (Greece)

In recent years {alpha}-{gamma} coincidence experiments at 136 MeV incident energy on {sup 48}Ca, {sup 140}Ce, {sup 138}Ba and {sup 124}Sn were performed at the KVI in Groningen to study the isospin character of electric dipole excitations below the particle threshold, frequently called Pygmy Dipole Resonance (PDR). An array of HPGe {gamma}-detectors has been used in coincidence with the Big-Bite Spectrometer (BBS) and a resolution of about 10 keV in the {gamma}-ray energy has been achieved. The results show that the excitation patterns of the PDR in the ({alpha},{alpha}') reaction seem to differ significantly from results obtained in Nuclear Resonance Fluorescence (NRF)({gamma},{gamma}') measurements. The PDR, which until now has been assigned to one excitation mode, splits up into two parts: One that is excited in ({alpha},{alpha}'{gamma}) and ({gamma},{gamma}') reactions (denoting a dominant isoscalar character), and one that is only excited in ({gamma},{gamma}')(denoting a dominant isovector character). This indicates that two different excitation mechanisms produce these low-lying E1 excitations [1], The preliminary results of the latest measurements on the N = 82 nucleus {sup 138}Ba and the Z = 50 nucleus {sup 124}Sn show that this break up into two parts is a common feature of the PDR in semi-magic nuclei.

• OSTI ID: 21255440
• Journal Information: AIP Conference Proceedings, Vol. 1090, Issue 1; Conference: 13. international symposium on capture gamma-ray spectroscopy and related topics, Cologne (Germany), 25-29 Aug 2008; Other Information: DOI: 10.1063/1.3087045; (c) 2009 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0094-243X
• Country of Publication: United States
• Language: English

Related Subjects

73 NUCLEAR PHYSICS AND RADIATION PHYSICS
ALPHA PARTICLES
ALPHA REACTIONS
BARIUM 138
CALCIUM 48
CERIUM 140
COLLECTIVE MODEL
DOPPLER EFFECT
ELECTRIC DIPOLES
EXCITATION
GAMMA RADIATION
ISOSPIN
ISOVECTORS
MAGIC NUCLEI
MEV RANGE 100-1000
PHOTONUCLEAR REACTIONS
RESONANCE FLUORESCENCE
SPECTROMETERS
TIN 124