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Bochum 1998 – wissenschaftliches Programm

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HK: Hadronen und Kerne

HK 70: Plenar

HK 70.3: Gruppenbericht

Freitag, 20. März 1998, 12:30–13:00, P

Electric dipole excitations in semi magic nuclei studied in photon scattering experiments — •R.-D. Herzberg1, J. Bryssinck2, L. Govor3, D. Belic4, F. Bauwens2, O. Beck4, P. von Brentano1, D. De Frenne2, J. Eberth1, T. Eckert4, J. Enders5, A. Fitzler1, C. Fransen1, K. Govaert2, E. Jacobs2, L. Kaeubler6, H. Kaiser5, U. Kneissl4, A. Linnemann1, H. Maser4, P. Matschinsky1, P. von Neumann-Cosel5, A. Nord4, N. Pietralla1, H.H. Pitz4, V.Yu. Ponomarev7, H. Prade6, E. Radermacher1, A. Richter5, H. Schnare6, R. Schwengner6, O. Thelen1, H.G. Thomas1, H. Tiesler1, V. Werner1, D. Weisshaar1, I. Wiedenhöver1, M. Wilhelm1, and A. Zilges51Inst. f. Kernphysik, Universit"at zu K"oln, D-50937 K"oln — 2Vakgroep Subatomaire en Stralingsfysica, University Gent, 9000 Gent, Belgium — 3Russian Scientific Centre “Kurchatov Institute”, Moscow, Russia — 4Inst. f. Strahlenphysik, Universit"at Stuttgart, D-70569 Stuttgart — 5Inst. f. Kernphysik, TU Darmstadt, D-64289 Darmstadt — 6Inst. f. Kern- und Hadronenphysik, FZ Rossendorf, D-01314 Dresden — 7Bogoliubov Laboratory of Theoretical Physics, JINR, Dubna, Russia

Nuclear Resonance Fluorescence (NRF) experiments on 116,118,120,122,124Sn including linear polarization measurements have been carried out at the Dynamitron accelerator in Stuttgart and the linac of the University of Gent [1] to study two phonon quadrupole-octupole excitations. The systematical behavior of the energies and excitation strengths of the strongly excited two phonon 1 states agrees well with that of the two phonon states in the N=82 isotones [2]. The quadrupole octupole two phonon character of these excitations in N=82 nuclei has been proven only recently through the detection of the decay strength to the one phonon states [3]. High energy NRF experiments on 116,124Sn using polarized bremsstrahlung in Gent and the N=82 isotones 140Ce [4] and 138Ba using the Cluster detector as a Compton polarimeter at the S-DALINAC in Darmstadt show a concentration of E1 strength above 5 MeV, which are well reproduced by QPM calculations. The total excitation strength of the two phonon states stems from a delicate interplay of the main two phonon component and a small admixture of the GDR.
Supp. by the DFG Nos. Kn-154/30, Br-799/6-2, Ri-242/12-1, BMBF Nos. 06DA665I, 06DR666I, 06OK862I(O) and by FSR-Flanders.
[1] K. Govaert et al., Phys. Lett. B335, (1994), 113; and J. Bryssinck et al. Proceedings of the Dubna Conference 1997.
[2] R.-D. Herzberg et al., Nucl. Phys. A592, (1995), 211.
[3] M. Wilhelm et al., Phys. Rev. C54, (1996), R449.
[4] R.-D. Herzberg et al., Phys. Lett. B390, (1997), 49.

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