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Siddhartha Dechoudhury

Publications and source records attributed to Siddhartha Dechoudhury.

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Empirical formalism for the production of neutron-rich nuclei using fragmentation of medium heavy neutron-rich Rare Isotope Beam

We report here an empirical formalism for predicting the cross-sections of neutron-rich nuclei produced in fragmentation of relativistic \b{eta}-unstable neutron-rich projectiles in the mid-mass region. The formalism is based on the abrasion-ablation picture of the projectile fragmentation reaction. It has been shown that the formalism can accurately reproduce the experimental cross-section data for nuclei produced in the fragmentation of 132Sn. The formalism, it is shown, can also reproduce the experimental cross-sections of neutron-rich nuclei produced in the fragmentation of 129Xe fairly accurately. The formalism is used to bring out the advantage in the production cross-sections of neutron-rich isotopes, especially the more neutron-rich ones; that one can expect by using unstable doubly magic neutron-rich projectile 132Sn as compared to comparatively less neutron-rich unstable projectile 128Sn and also 124Sn, the isotope which is most neutron-rich among the stable isotopes of Sn (tin). The formalism is used to predict the cross-sections of neutron-rich nuclei produced in the fragmentation reaction of unstable 144Xe and 146Cs, which are expected to be produced with sufficient intensity in the upcoming RIB facilities and in the existing RIB facilities after beam intensity upgrade.

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Signature of bi-modal fission in Uranium nuclei

We report here the signature of bi-modal fission, one asymmetric and the other symmetric, in Uranium nuclei in the mass range A = 230 to 236. The finding is unexpected and striking and is based on a model independent analysis of experimental mass distributions (cumulative yields) at various excitations from about 23 to 66 MeV in the alpha induced fission of 232Th. It has been found that the observed asymmetry in the mass distributions and the unusually narrow peak in the symmetry region, can both be explained in a consistent manner if one assumes: a) multi-chance fission, b) bi-modal fission at lower excitations (9 < E* < 25 MeV) for all the Uranium nuclei in the range A = 230 to 236, and c) that the shell effects get washed out completely beyond about 25 MeV of excitation resulting in symmetric fission. The analysis has allowed a quantitative estimation of the percentages of the asymmetric and the symmetric component in the bi-modal fission. It has been found that the bi-modal fission in Uranium nuclei is predominantly asymmetric (~ 85%), which contributes in a major way to the observed asymmetric peaks, while the ~15% bi-modal symmetric fission is primarily responsible for the observed narrow symmetric peak in the mass distributions. The unusually narrow symmetry peak in the mass distributions indicates that the symmetric bi-modal fission in Uranium nuclei must have proceeded from a configuration at the bi-modal symmetric saddle that is highly deformed with a well-developed neck.

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