Bochum 1998 – scientific programme
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HK: Hadronen und Kerne
HK 70: Plenar
HK 70.3: Group Report
Friday, March 20, 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. Zilges5 — 1Inst. 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.