Study of the Pygmy Dipole Resonance in 124Sn by means of the (α,α'γ)(α,α′γ) reaction

J. Endres, A. Zilges, N. Pietralla, D. Savran, K. Sonnabend, M. N. Harakeh, V. I. Stoica, H. J. Wortche, P Butler, R. -D. Herzberg, Marcus Scheck, R Krucken, L. Popescu, S. Harissopulos, A. Lagoyannis

Research output: Chapter in Book/Report/Conference proceedingConference contribution

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Abstract

In recent years α−γα−γ coincidence experiments at 136 MeV incident energy on 48Ca,140Ce, 138Ba and 124Sn 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 γ‐detectors has been used in coincidence with the Big‐Bite Spectrometer (BBS) and a resolution of about 10 keV in the γ‐ray energy has been achieved. The results show that the excitation patterns of the PDR in the (α,α')(α,α′) reaction seem to differ significantly from results obtained in Nuclear Resonance Fluorescence (NRF) (γ,γ')(γ,γ′) measurements. The PDR, which until now has been assigned to one excitation mode, splits up into two parts: One that is excited in (α,α'γ)(α,α′γ) and (γ,γ')(γ,γ′) reactions (denoting a dominant isoscalar character), and one that is only excited in (γ,γ')(γ,γ′) (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 138Ba and the Z = 50 nucleus 124Sn show that this break up into two parts is a common feature of the PDR in semi‐magic nuclei.
Original languageEnglish
Title of host publicationCapture Gamma‐ray Spectroscopy and Related Topics
Subtitle of host publicationProceedings of the 13th International Symposium on Capture Gamma‐ray Spectroscopy and Related Topics
EditorsJan Jolie, Andreas Zilges, Nigel Warr, Andrey Blazhev
PublisherAIP Publishing
Volume1090
ISBN (Print)978-0-7354-0623-0
DOIs
Publication statusPublished - 28 Jan 2009
Externally publishedYes
EventProceedings of the XIIIth International Symposium - Cologne, Germany
Duration: 25 Aug 200829 Aug 2008

Publication series

NameAIP Conference Proceedings
ISSN (Print)0094-243X
ISSN (Electronic)1551-7616

Conference

ConferenceProceedings of the XIIIth International Symposium
CountryGermany
CityCologne
Period25/08/0829/08/08

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Endres, J., Zilges, A., Pietralla, N., Savran, D., Sonnabend, K., Harakeh, M. N., Stoica, V. I., Wortche, H. J., Butler, P., Herzberg, R. -D., Scheck, M., Krucken, R., Popescu, L., Harissopulos, S., & Lagoyannis, A. (2009). Study of the Pygmy Dipole Resonance in 124Sn by means of the (α,α'γ)(α,α′γ) reaction. In J. Jolie, A. Zilges, N. Warr, & A. Blazhev (Eds.), Capture Gamma‐ray Spectroscopy and Related Topics: Proceedings of the 13th International Symposium on Capture Gamma‐ray Spectroscopy and Related Topics (Vol. 1090). [357] (AIP Conference Proceedings ). AIP Publishing. https://doi.org/10.1063/1.3087045