Microscopic calculations for upper-fp,g9/2 shell nuclei: Ge & Se

J. P. Draayer, Louisiana State University
K. P. Drumev, Louisiana State University


Shell-model calculations for isotopes of Ge and Se are reported where valence nucleons beyond the N = 28 = Z core occupy levels ofthe normal parity upper-fp shell (f5/2,p3/2,p1/2) and the unique parity g9/2 intruder configuration. Results are given for realistic interactions of the Kuo-Brown-3 type with various model space truncations that key in on the number of nucleon pairs allowed to occupy the intruder level. Electromagnetic (E2 & M1) rates as well as decay probabilities are calculated, some of which are key in determining the structure of "waiting point" nuclei that regulate certain nucleo-astrosynthesis processes. The role of the intruder level, which istreated on an equal footing with the normal parity levels, is shown to be important for reproducing structural details. The levels of the upper-fp shell are handled within the framework of a normal ls-coupled basis as well as its pseudo-SU(3) counterpart, and respectively, the g9/2 as a single level and as a member for the complete gds shell. The second of these two approaches, namely, the SU(3) picture, allows one to better probe the effect of deformation. © EDP Sciences/Societé Italiana di Fisica/Springer-Verlag 2007.