IBMF and IBFFM Approach to Nuclei in the A≃100 Region

Abstract

An overview of the calculations in IBFM and IBFFM for nuclei in the A .. 100 region is presented. The application to these nuclei with a complex structure including the rapid transition from spherical to deformed nuclear shapes provides a stringent test for the capacities of this theoretical approach. From the result of the studies of the heavy Yttrium isotopes and the N=59 isotones it is concluded that it can account for the basic structure and the phase transition in these nuclei.

Structure of the Triplet of low-lying states in101Mo

“…This is in accordance with the observation that the d3/2 quasiparticle state is not close [12] to the Fermi surface in this mass region. Next we note that the features (la, b, d) also exclude the possibility to interpret the low-lying triplet in l~ as the IBFM anomalous triplet of states J= j=5~2, J=j--l=3/2, J=j-2=l/2, associated with a d3/2 quasiparticle configuration.…”

“…This result follows the trend predicted by the BCS approximation. Let us compare the present parametrization to the previous calculation [30] with parametrization L There was assumed that the states of the two different types in the core nucleus m~ can be described in an average way by a single set of renormalized IBM parameters. Obviously, this implies a rather drastic approximation since the two sets of states resemble the O (6) and SU (5) limits of IBM, respectively.…”

“…3a, to the 0(6) subset of experimental levels in ~~176 The grouping of the levels into the 0(6) and SU(5) subsets follows [37] and preliminary data from [43]. b Calculated low-lying positive-paritystates of tmMo in comparison with the experimental levels earlier one (parametrization I of [30]), is discussed later. The corresponding core parameters, given in MeV, are h1=0.45, h2=-0.15, h3=0.007, h40=h44=0, h42= -0.12 which is a somewhat distorted O (6) type of parametrization.…”

“…Next we note that the features (la, b, d) also exclude the possibility to interpret the low-lying triplet in l~ as the IBFM anomalous triplet of states J= j=5~2, J=j--l=3/2, J=j-2=l/2, associated with a d3/2 quasiparticle configuration. A first calculation on l~ along this line ofJ = j-2 parametrization was performed (parametrization II of [30]) similar to that for the heavier N= 59 isotone l~ [31]. As for this case, in l~ the c75/2 quasipartMe is the lowest-lying one.…”

“…Recently, calculations for odd-even nuclei [11,12] and for odd-odd nuclei [12,13] in the region around A = 100 have been performed successfully in the framework of the interacting boson-fermion model (IBFM) and the interacting boson-fermion-fermion model (IBFFM), respectively. Therefore, the IBF model in the equivalent representation of the particle-truncated quadrupole-phonon coupling model (PTQM) has now been applied to 1~ In particular, the studies aimed at answering the question whether the ground-state is of the (d5/2)~/2; j-2 type, similar to the 167 keV 3/2 + state in the isotone 97Sr which according to IBFM calculations contains a strong component of the configuration 3 (g7/~)3/2.…”