Search

The cross over of β-, and γ-band at N = 94 in 158Gd signifies a major change in the nuclear structure of Gd isotopes. Using the microscopic dynamic pairing plus quadrupole (DPPQ) model, we reproduce this transition. The spectral features of the K π = 0 3 + , 2 1 + and 4 1 + bands besides the lower three: ground, β- and γ-bands have been analyzed. The B(E2) values from the K π = 0 2 + and K π = 0 3 + bands are analyzed to interpret the nature of these two bands. The K π = 0 2 + band is confirmed as the axially symmetric β-vibration. The K π = 0 3 + band is shown to be collective vibration, but instead of 2β vibration, it indicates very special features with large anharmonicity. The five excited 0 + states below 2.0 MeV identified in 158Gd from ( p , t ) reaction work are also predicted from the DPPQ model. The relative variation of β- and γ-band head energies and of K π = 0 3 + bands, and of K π = 4 + band with neutron number N in 152 - 160 Gd isotopes is reproduced. But the vibrational energy scale of the excited bands remains expanded. The algebraic interacting sd-boson model is also applied for evaluating the energy spectrum and the B(E2) ratios in these K-bands and for prediction of the multi-phonon 0 + states.

The spectra of the isotopes of Zn, Ge and Se in the A = 60 – 80 region of the nuclear landscape display interesting spectral variations with N and Z. At first we study these structures empirically. The state-wise deformation status of each isotope is deduced using the power index formula. The average value of the power index displays the variation with neutron number N. The linear plot of B ( E 2 , 0 1 + → 2 1 + ) versus [ 1 / E ( 2 1 + ) ] for a given Z gives further information on the spectral variation with N. The level energy spectra are used to study the role of the excited bands in the phase transitions and the possible shape co-existence. The common spectral features of the three isotopic chains and some unique features are pointed out from our study and the role of the Nilsson single particle orbits is discussed. A comparison with recent works for Ge and Se isotopes reveals the importance of our empirical studies vis-a-vis the high efficiency experiments and different theoretical interpretations of the shape changes with N and Z and spin.

The constancy of the Grodzins product (GP) E ( 2 1 + ) × B ( E 2 ) ↑ , implies independence from the vibration–rotation status of the nucleus, after allowing for the Z and A dependence. However, in some recent studies, the correlation of the variation of GP, with some collective entities like the N p N n product have been pointed out. This anomaly of the constancy of the GP versus the variation is reviewed here. Detailed analysis of these applications for the violation of the GPR pointed out in these studies is given. Comparison is also made with the linearity relation of B ( E 2 ) ↑ versus 1 / E ( 2 1 + ) plots for a few elements, which provide a simple view of the GP variation with N and Z. The basic physics underlying this rule is presented.

Low lying states of 150Sm have been studied through decay spectroscopy of odd–odd 150Pm, populated with 150Nd(p, n)150Pm reaction at E b e a m = 8.0 MeV using 97% enriched 150Nd target and detecting the γ-rays with the VENUS array comprised of six Compton suppressed Clover HPGe detectors. Nineteen new transitions are placed, four tentative γ-rays are confirmed and eight transitions are found to have altered placements; consequently assigning thirteen new levels to the decay scheme of 150Pm. The spin-parity assignments of the excited levels of 150Sm were made based on logft and angular correlation analysis.

The Xe isotopes in the A = 130 region, with low quadrupole deformation β , are good examples of the γ -soft nuclei. Recent data of 124 Xe exhibit well developed K -bands of ground, K π = 2 1 + , 0 2 + , 0 3 + and 4 1 + . Its spectrum is studied in relation to the underlying dynamic symmetries. The absolute intra- and inter-band B ( E2 ) values and the B ( E2 ) ratios are compared with the theoretical predictions of the dynamic pairing plus quadrupole model in the microscopic approach, and the interacting boson model IBM-1. The potential energy surface illustrates the γ -soft character. The variation of inertia tensor over the ( β , γ ) space is studied, and the spread of the wave functions of three I π = 0 + and two 2 + states over the ( β , γ ) space illustrate their varied character. Comparison is done with the dynamic symmetries of IBM for different bands. The O(6) symmetry breaking and preservation of the O(5) and O(6) symmetry are reviewed.

The level structures of 130–136Ce are analyzed with the available experimental data. The level energies, E2 moments and the B ( E 2 ) ratios for transitions from the K = 2 and 02 bands are compared with the values from the Dynamic Pairing plus Quadrupole model and the Interacting Boson Model-1. In 130Ce, the recently assigned 1.672 MeV I = ( 2 , 3 , 4 ) + state is tentatively associated with I = 4 on the basis of the predicted K-components and the decay mode. The 2.068 MeV I = ( 4 , 5 , 6 ) + state is associated with 5 2 + of this K = 4 band. In 132Ce, the 1932 keV I = 4 level is associated with K π = 0 2 + band. Variation of the nuclear structure with neutron number N is studied vis-a-vis the O ( 6 ) symmetry and critical point symmetries X ( 5 ) and E ( 5 ) . The effect of filling of up-sloping Nilsson orbitals on the decreasing deformation with increasing N is illustrated.

The dynamic pairing plus quadrupole model is used to study the changes in nuclear structure of N =66 isotones of Mo–Sn–Ce. Two different single-particle configurations have been used for Z Z ⩾50 regions and their suitability for respective regions is illustrated. The variations with Z of the quadrupole deformation β , deformation energy E d , and the 2 1 + state energy, B (E2;0 + →2 + ) and quadrupole moment Q (2 + ) are reproduced. The role of the spin–orbit partner (SOP) orbitals in n–p interaction for inducing the deformation in each region is studied.

The dynamic pairing plus quadrupole model of Kumar and Baranger is employed for studying variations of the nuclear structure of light Ba isotopes with A =122–134. The potential energy surface parameters have been calculated and the low-spin level spectrum is predicted along with the static and transition E2 moments. Comparison with experiment and with other theories supports the validity of our treatment.

The level structures and grouping into K -bands of 158 Dy and 160 Dy are calculated in the dynamic pairing-plus-quadrupole model. The analysis is extended to five K -bands with I π ⩽ 6 + . The rise of the 0 2 + and 0 3 + states with N in 154–160 Dy and the crossing of 2 β over 2 γ at 158 Dy are reproduced. The calculated absolute E2 moments, relative B (E2) values for interband transitions and X (E0/E2) are compared with experimental data.