Search

Treating the energy of the 21+ state in even Z- even N nuclei as a sum of rotational energy (ROTE) and vibrational energy (VIBE), the evolution of the shape transition with the increase in the valence nucleon pairs product (Np Nn) is studied via the variation of ROTE/E(21+). The correspondence of relative ROTE, B(E2)↑ and (βdef/βs.p.) values vs. the Np Nn product is illustrated. A correlation of the Rotation-Vibration interaction constant in the ground band levels with the 0β+ energy is also derived. Comparison is made with variable moment of inertia model expressions.

A single term expression in the form of a Power law with two unknown coefficients is proposed. It explains fairly well the energies of ground bands in even-even nuclei in the A = 150-200 region. The index b and the coefficient a in this expression are fairly constant independent of the level spin, below the back bending energy. Variation of average a and b with Z and N, and with the valence nucleon pair product Np Nn is also illustrated and agrees with general expectations.

The proton neutron interacting boson model (IBM-2) has been used to make a systematic study of Strontium isotopes in this mass region of A ~ 80 with 38 N 48 and Z = 38. The three-term Talmi–Otsuka general Hamiltonian in the framework of the neutron proton version of the Interaction boson model was used to perform the calculations. The yrast levels energy are reproduced. The beta and gamma band energy levels also matched well. The reduced transition probabilities were also calculated and were found to be in agreement with the experimental values. In addition, g-factor for the state was evaluated. Possible candidates for mixed symmetry states were also predicted for several nuclei in this isotopic chain.

The experimental data of interband γ-g B(E2) ratios for even-even light Te-Sm nuclei (66 ≤ N ≤ 78) is compared with the predictions of the rigid triaxial model to search for a correlation between the nuclear structure variation with the asymmetry parameter γ0 of the model.

A two-parameter single-term energy formula E J =aJ b is used to study the energy–spin relationship in the ground bands of even–even light Xe–Gd (68⩽N⩽78) nuclei. This formula works better for soft nuclei as well as for deformed nuclei. We also compared it with other two-parameter formulae, i.e. Ejiri, ab, pq and Brentano et al soft rotor (SRF) formulae. The power index b and the coefficient a are fairly constant, independent of the number of levels for spin J⩽12+. The variation of average and with Z, N and with the valence nucleon pair product N p N n is illustrated. Extension of the formula to E J =aJ (b+cJ) is also tested.

The recent extension of the energy spectrum of 156Gd to include up to five Kπ = 0+, two Kπ = 2+ and two Kπ = 4+ rotational bands from an (n, γ) reaction study allows further tests of the validity of the dynamic pairing-plus-quadrupole model of nuclei. Eight of these rotational bands are obtained in the model, though the calculated energy scale is much expanded. Their decay characteristics are compared with experiment.

Uptodate accurate extensive data on γ-g B(E2) ratios for even-even rare-earth nuclei is compared with the predictions of the rigid triaxial model of collective rotation to search for a correlation between the nuclear structure variation with Z, N and the γ0 parameter of the model. The internal consistency in the predictions of the model is investigated and the spectral features vis-a-vis the γ-soft and the γ-rigid potential are discussed.