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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 ^{116,118,120,122,124}Sn 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.