Freiburg 1999 – scientific programme
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HK: Physik der Hadronen und Kerne
HK 19: Kernphysik III / Magnetische Momente
HK 19.1: Group Report
Tuesday, March 23, 1999, 14:00–14:30, B
Lifetime and magnetic moment measurements in the shell model nucleus 4494Ru — •A. Jungclaus1, D. Kast1, K.P. Lieb1, C. Teich1, M. Weiszflog1, T. Härtlein2, C. Ender2, F. Köck2, D. Schwalm2, J. Reif3, I.P. Johnstone4, J. Eberth5, H.G. Thomas5, R. Peusquens5, A. Dewald5, H. Grawe6, and M. Górska6 — 1II. Physikalisches Institut, Universität Göttingen, Bunsenstr. 7-9, D-37073 Göttingen — 2Max-Planck-Institut für Kernphysik, D-69029 Heidelberg — 3Institut für Kern- und Hadronenphysik, FZ Rossendorf, D-01314 Dresden — 4Department of Physics, Queen’s University, Kingston, Canada — 5Institut für Kernphysik, Universität zu Köln, Zülpicherstrasse, D-50937 Köln — 6GSI, Darmstadt
In the semi-magic N=50 nuclei 4494Ru and 4595Rh, the low-energy parts of the excitation schemes reflect the various valence proton configurations within the (p1/2,g9/2) space. In contrast, states with spins higher than 12+, 13− in 94Ru and 25/2+, 25/2− in 95Rh are assumed to be generated by raising a neutron from the g9/2 across the N=50 shell gap into the d5/2 orbit [1]. To prove these predictions and to further investigate the role of the lower-lying orbits (f5/2, p3/2) in the intermediate spin range precise lifetimes in the range from 0.5 to 40 ps were determined in both nuclei by means of the RDDS technique and the reaction 58Ni + 40Ca at 145 MeV. Whereas the results for 95Rh have already been presented in [2], we will report here on the experimental electromagnetic transition strengths obtained for 94Ru. Both the excitation energies and transition rates are compared to large-scale shell model calculations using different configuration spaces and residual interactions [2,3]. At negative parity, the experimental 132−, 141−, and 151− states could be identified as pure proton states with the configuration π(g9/2)5 π(f5/2). The agreement between experiment and calculations is excellent. Furthermore, it was found that due to the particle-hole symmetry within the g9/2 shell, the structure of the π=- yrast states in 95Rh is equivalent to that of the corresponding π=+ levels in 94Ru plus a p1/2 proton [ 95Rh− = 94Ru+ ⊗ π(p1/2) ] and vice versa. To complete the experimental information in the two N = 50 nuclei, g-factors of excited states with lifetimes between 20 ps and 1 ns were determined via the IMPAD method after recoil implantation into ferromagnetic Fe and Ni hosts. Both experiments reported on have been performed at the MPI Heidelberg.
[1] H. A. Roth et al., Phys. Rev. C50 (1994) 1330.
[2] A. Jungclaus et al., Nucl. Phys A637 (1998) 346.
[3] I. P. Johnstone and L. D. Skouras, Phys. Rev. C55 (1997) 1227.