In the Interacting Boson-Fermion-Fermion Model (IBFFM) for odd-odd nuclei the yrast states are calculated for\(\tilde j_\pi = \tilde h_{1 1/2} ,\tilde j_v = \tilde i_{1 3/2} \), proton-neutron configurations coupled to theO(6) andSU(3) boson core. The results are discussed in terms of the strongly coupled/ decoupled band type criterion and in comparison to the peaceful and conflicting case of asymmetric rotor model.

IBFFM yrast states in odd-odd nuclei associated withO(6) andSU(3) limits

We present a method to calculate spectroscopic properties of odd-odd nuclei within the framework of the interacting boson-fermion-fermion model (IBFFM

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Spectroscopy of odd-odd nuclei within the interacting boson-fermion-fermion model based on the Gogny energy-density functional

A band with a rotational pattern based on a state at 585.1 keV has been identified in theN=59 neutron-rich nucleus97Sr. Its properties lead to the [422] 3/2 Nilsson-orbital assignment for the band head. There is evidence for a second band with the head at 644.7 keV and the configuration [541] 3/2. Since the ground state and the lowest excited levels are spherical, shape coexistence is established for97Sr. A deformed nature of several levels at 500–600 keV results also from QRPA-model calculations. The structure of the low-lying spherical levels has been studied in the frame of the IBF model. The results of the present investigations lead to a better understanding of theN=59 isotones which constitute the link between the spherical and deformed nuclei atA∼100 as a species with shape coexistence but without any indications of particular softness.

Structure of theN=59 nucleus97Sr: coexistence of spherical and deformed states

The structure of the nucleus
 39
 96
 Y57 is discussed in the framework of the parabolic rule for the splitting of members of proton-neutron coupled configurations and of the interacting boson-fermion-fermion model (IBFFM). A good description of the available experimental data including the existence of theβ
− decaying 8+ isomer with a half-life of 10 s has been obtained which demonstrates the influence of the subshell closures in the neighbourhood of
 40
 96
 Zr56.

Proton-neutron multiplets in 96 Y

The quantal analogs of the Gallagher-Moszkowski bands in the Interacting boson-fermion-fermion model (IBFFM) withSU (3) boson core are associated with the exact quantum numberKjp+jn and approximate quantum numberK-¦jp-jn¦ of IBFFM. For characteristic ratiosГ/δ it is shown that theKc=0 band in even-even IBM system, theK=jp andK=jn bands in the corresponding odd-even (IBFM) systems and theK=jp+j band in the corresponding odd-odd IBFFM system exhibit the supermultiplet pattern.

Analogs of Gallagher-Moszkowski Bands in IBFFM- A Relation to Spectrum-Generating Supersymmetry?

The levels of198Au have been calculated in IBFFM as a first application of the new model for odd-odd nuclei. The study of the Au (n, γ) spectrum has led to a large amount of data on the odd-odd nucleus198Au, with spin/parity assignments of numerous low-lying states /l/. In particular, fifteen 1−, 2− levels have been found below 500 keV. However, at that time a detailed comparison with nuclear structure theory was not possible. In last decade, the interacting boson model was extensively applied to description of even-even and odd-even nuclei /2,3/. Only recently, this approach was extended to odd-odd nuclei /4–8/. A new model /4,5/ for odd-odd nuclei was introduced, referred to as IBFFM or OTQM. In related development, a few dynamical symmetries and supersymmetries have been introduced, which encompass odd-odd nuclei. These supersymmetries are associated with Uν (6/4)×Uπ (6/4) /6/, Uν(6/12)×Uπ (6/4) /7/ and with a symplectic chain /8/.

Odd-odd nucleus 198 Au as first test of IBFFM (OTQM)

Four related algebraic approaches to odd-odd nuclei are described. Results of recent calculations are given, and possible extensions and current problems are discussed

A. B. Balantekin

Papers

Odd-odd nucleus 198 Au as first test of IBFFM (OTQM)

Algebraic and supersymmetric treatment of odd-odd nuclei