Splitting of the pygmy dipole resonance

J. Endres, P. Butler, M. N. Harakeh, S. Harissopulos, R-D. Herzberg, R. Kruecken, A. Lagoyannis, E. Litvinova, N. Pietralla, V. Yu. Ponomarev, L. Popescu, P. Ring, D. Savran, M. Scheck, K. Sonnabend, V. I. Stoica, H. J. Wörtche, A. Zilges

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


In recent years investigations have been made to study the electric Pygmy Dipole Resonance (PDR) systematically, mainly in semi‐magic nuclei. For this purpose the well understood high resolution (γ,γ′) photon scattering method is used. In complementary (α,α′γ) coincidence experiments at Eα = 136 MeV a similar γ‐energy resolution and a high selectivity to E1 transitions can be obtained at the Big‐Bite Spectrometer (BBS) at KVI, Groningen. In comparison to the (γ,γ′) method a structural splitting of the PDR is observed in the N = 82 nuclei 138Ba and 140Ce and in the Z = 50 nucleus 124Sn. The low energy part is excited in (γ,γ′) as well as in (α,α′γ) while the high energy part is observed in (γ,γ′) only. The experimental results together with theoretical QPM and RQTBA calculations on 124Sn which are able to reproduce the splitting of the PDR qualitatively are presented. The low‐lying group of Jπ = 1⎯ states seem to represent the more isoscalar neutron‐skin oscillation of the PDR while the energetically higher‐lying states seemingly belong to the transitional region between the PDR and the isovector Giant Dipole Resonance (IVGDR).
Original languageEnglish
Title of host publicationFrontiers in Nuclear Structure, Astrophysics and Reactions
Subtitle of host publicationFINUSTAR 3, Rhodes, Greece, 23-27 August 2010
EditorsParaskevi Demetriou, Rauno Julin, Sotirios Harissopulos
PublisherAIP Publishing
ISBN (Print)978-0-7354-0937-8
Publication statusPublished - 2011
Externally publishedYes

Publication series

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


  • PDR
  • QPM
  • nuclear reactions
  • Sn-124(alpha, alpha 'gamma)


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