The 6

No abstract

In the nuclear f 7/2 shell, the nucleon-nucleon interaction can be represented by the eight values E(J ) = (f 2 7/2 ) J |V |(f 2 7/2 ) J , J = 0, 1, . . . , 7, where for even J the isospin is 1, and for odd J it is 0. If we set the T = 0 (odd J ) two-body matrix elements to zero (or to a constant), we find several degeneracies that we attempt to explain in this work. We also give more detailed expressions than previously for the energies of the states in question. New methods are used to explain degeneracies that are found in 45 Ti (I = 25/2 − and 27/2 − ), 46 V (I = 12 + 1 and 13 + 1 , as well as I = 13 + 2 and 15 + ), and 47 V (I = 29/2 − and 31/2 − ).

In this work we look at the low lying nuclear structure of several N = Z nuclei residing between the doubly magic nuclei 40 Ca and 100 Sn. Using large shell model codes, we calculate and discuss the systematics of energies. We show energy levels, B(E2)'s, static quadrupole moments and g factors. In all cases, we compare the results of two different interactions which yield significantly different occupation numbers. We compare with the simplest versions of the rotational and vibrational models. By examining B(E2)'s and static quadrupole moments, we make associations with collective models and find that, in the model space here considered, 88 Ru is oblate. The quadrupole moment of 92 Pd is very small, consistent with the vibrational model.

In this work we examine two recent effective shell model interactions, JUN45 and JJ4B, that have been proposed for use in the f 5/2 , p 3/2 , p 1/2 , g 9/2 model space for both protons and neutrons. We calculate a number of quantities that did not enter into the fits undertaken to fix the parameters of both interactions. In particular we consider static quadrupole moments (Q's) of excited states of the even-even 70−76 Ge isotopes, as well as the B(E2) values in these nuclei. (We have previously studied 70 Zn isotopes using JJ4B.) Some striking disagreements between the JUN45 prediction and the experimental results had already been noted for the quadrupole moments of the 2 + 1 states of these nuclei. We investigate whether these discrepancies also occur for the JJ4B interaction. Subsequently, we also apply both interactions to calculate the Q's of some more highly excited states and compare the two sets of predictions regarding the nature of the nuclear states under consideration. In order to gain insight into these more complex large-scale shell-model calculations, we examine the corresponding and much simpler single-j shell model calculations in the g 9/2 neutron shell.PACS numbers: