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The excitation energy difference (ΔE) between the terminating states built on the f7/2n and d3/2-1f7/2n+1 configurations (here, 'n' denotes the number of valence particles outside the 40Ca core and the particle hole excitation across the magic gap 20 is of proton type) in the lower fp shell are studied systematically within the framework of the cranked relativistic mean field model. The ΔE thus defined, depends predominantly on the f7/2 - d3/2 shell gap, and its evolution as a function of neutron - proton asymmetry. The latter, in turn, depends on the isoscalar - isovector balance in the spin - orbit potential. Therefore, a systematic investigation of the difference ΔE is expected to test quantitatively the predicted shell gaps as a function of isospin. We find that: 1) the conventional NL3 parameter set over estimates the ΔE values, implying that the said shell gap is over - estimated in this parametrization and 2) the largest deviation between the calculated and the experimental values of ΔE is obtained for the nucleus with the smallest asymmetry value in the set of nuclei considered, and that the deviation decreases with increasing asymmetry, indicating that the in RMF parametrization considered, the isoscalar - isovector balance in the spin - orbit potential requires improvement. We carry out a re - fit of the RMF parameters to attempt a remedy to these two problems. We find that in addition to the binding energies and charge radii, if a constraint is put on the f7/2 - d3/2 shell gap in the fit to the Lagrangian parameters, the overall agreement of ΔE with the experiment improves significantly, without disturbing the agreement already achieved for the bulk properties of the nuclei spanning the entire periodic table. At a finer level, however, it is found that the isoscalar - isovector balance in the spin orbit interaction is required to be improved further. A detailed work in this direction is in progress. [ABSTRACT FROM AUTHOR]

The recently proposed microscopic - macroscopic model for nuclear masses, based on the shell corrections obtained by using the semi - classical Wigner - Kirkwood (WK) h expansion of one body quantal partition function, has been extended to the even - even deformed nuclei. The nuclear potential is assumed to be deformed Woods - Saxon with spin - orbit contribution. The Coulomb potential is obtained by folding charge densities. The resulting partition function is expanded upto the fourth order in h to obtain averaged energies. The shell corrections thus obtained along with pairing energies determined within the framework of the Lipkin - Nogami scheme constitute microscopic part of the model. The macroscopic part is obtained from a liquid drop formula, with nine adjustable parameters. These parameters are fitted by considering a large set of 561 even - even nuclei with Z ≥ 8 and N ≥ 8. The fit yields rms deviation of merely 610 keV from the corresponding experimental masses. A few applications of the mass formula are presented and discussed in this paper. [ABSTRACT FROM AUTHOR]

α formation amplitudes extracted from experimental data are presented and an abrupt change around the N = 126 shell closure is noted. It is explained as a sudden hindrance of the clustering of nucleons. The clustering induced by the pairing mode acting upon the four nucleons is inhibited if the configuration space does not allow a proper manifestation of the pairing collectivity. [ABSTRACT FROM AUTHOR]

We give a simple relation, connecting the logarithm of the half-life, corrected by the centrifugal barrier, with the Coulomb parameter in proton decay processes. The reduced experimental data lie on two straight lines as a result of a sudden change in the nuclear shape, marking two regions of deformation, divided by the charge number Z = 68. This feature provides a powerful tool to assign experimentally quantum numbers in proton emitters. [ABSTRACT FROM AUTHOR]

We propose a simple model for calculation of alpha decay hindrance factors. Using this model, we examine competing alpha decays populating several 0+ states in the daughter nuclei. These states have been described in the literature as belonging to different shapes. A scheme for calculation based on the Woods-Saxon model is developed. The deformation values are taken from potential energy surface calculations. Hence, no free parameters are introduced and only standard parameters of the Woods-Saxon potential are used. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

A new unified shell model scheme is introduced in which the single particle basis is a generalization of the Berggren representation. This repesentation includes virtual i.e. antibound basis states as well. We apply the new scheme to the ground state of the exotic nucleus 11Li. Here the antibound pole and the complex continuum both have large contributions and neither of them can be neglected. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]