Search

A description of the even-even Hf isotopes for A = 172 - 176 is carried out in the framework of the interacting boson model (IBM-1). The energy levels, B(E2) transition probabilities, electric quadrupole moment QL, and potential energy surface of those nuclei have been calculated. The calculated results are compared with the most recent experimental data. A good agreement for low lying energy states is obtained between experimental results and theoretical calculations. The contour plots of the potential energy surfaces show that the interested nuclei have rotational characters. [ABSTRACT FROM AUTHOR]

We describe α -transitions to low-lying states in even–even nuclei with Z > 50 , N > 82 using the Coherent State Model (CSM). We reproduce the energy levels and electromagnetic transition rates between the states of the ground band employing two parameters, namely the deformation parameter and the strength of the harmonic CSM Hamiltonian. The B(E2) values are described in terms of an effective charge which depends linearly on the deformation parameter. The treatment of the α -emission process is based on an α –daughter interaction containing a monopole component, calculated through a double folding procedure with a M3Y interaction plus a repulsive core simulating the Pauli principle, and a quadrupole–quadrupole (QQ) interaction. The decaying states are identified with the lowest narrow outgoing resonances obtained through the coupled channels method. The α -branching ratios to 2 + states are reproduced by means of the QQ strength. This interaction strength can be fitted with a linear dependence on the deformation parameter, as predicted by the CSM. The theoretical intensities to 4 + and 6 + states are in reasonable agreement with available experimental data. Predictions are made for spherical, transitional and well deformed even–even α -emitters. [ABSTRACT FROM AUTHOR]

Lifetime measurements of excited states in doubly-magic 56Ni have been performed exploiting the Doppler-shift attenuation method in order to determine reduced transition probabilities. For the 4 1 + and 6 1 + states, the deduced B (E2) values are compared with results from shell-model calculations employing the GXPF1A and the modern PFSDG-U interactions. In addition, valence ab-initio calculations were performed using a novel realistic Hamiltonian derived from chiral perturbation theory including three-body potential contributions and are confronted with the experimental findings. The new results show maximum E2 strength in comparison with known values along the N = 28 chain of isotones. The results corroborate the high collectivity for the double shell closure at N = Z = 28 which was anticipated from the large B (E2 ; 2 1 + → 0 g. s. +) value despite the considerable increase of its excitation energy as compared to neighboring semi-magic nuclei. Based on similarities in the shell structures of the self-conjugate doubly-magic nuclei 56Ni and 100Sn, the new values could be an indication for an expected comparable collective behavior of the 6 1 + state in 100Sn. [ABSTRACT FROM AUTHOR]