Understanding Nuclei in the upper sd - shell

Nuclei in the upper-$sd$ shell usually exhibit characteristics of spherical single particle excitations. In the recent years, employment of sophisticated techniques of gamma spectroscopy has led to observation of high spin states of several nuclei near A$\simeq$ 40. In a few of them multiparticle, multihole rotational states coexist with states of single particle nature. We have studied a few nuclei in this mass region experimentally, using various campaigns of the Indian National Gamma Array setup. We have compared and combined our empirical observations with the large-scale shell model results to interpret the structure of these nuclei. Indication of population of states of large deformation has been found in our data. This gives us an opportunity to investigate the interplay of single particle and collective degrees of freedom in this mass region.Comment: 8 pages, 13 figures, submitted for publication in the Proceedings of "Frontiers in Gamma-Ray Spectroscopy 2012 (FIG12), held at New Delhi, March 5th - 7th, 2012, Organized by Inter University Accelerator Center, New Delhi, Indi

Fusion cross sections for 6,7Li + 24Mg reactions at energies below and above the barrier

Measurement of fusion cross sections for the 6,7Li + 24Mg reactions by the characteristic gamma-ray method has been done at energies from below to well above the respective Coulomb barriers. The fusion cross sections obtained from these gamma-ray cross sections for the two systems are found to agree well with the total reaction cross sections at low energies. The decrease of fusion cross sections with increase of energy is consistent with the fact that other channels, in particular breakup open up with increase of bombarding energy. This shows that there is neither inhibition nor enhancement of fusion cross sections for these systems at above or below the barrier. The critical angular momenta (lcr) deduced from the fusion cross sections are found to have an energy dependence similar to other Li - induced reactions.Comment: 1 .pdf fil