arXiv subjects

Raj K. Gupta

Publications and source records attributed to Raj K. Gupta.

23 records · Page 2Linked to original sources

arXiv2003

A new semiempirical formula for exotic cluster decays of nuclei

A new semiempirical formula, with only three parameters, is proposed for cluster decay half-lives. The parameters of the formula are obtained by making a least square fit to the available experimental data. The calculated half-lives are compared with an other model-independent scaling law proposed earlier by Horoi {\it et al}. Also, the calculated results of this formula are compared with the recent results of the preformed cluster model for $^{12}$C and $^{14}$C emissions from different deformed and superdeformed Nd and Gd parents. The results are in good agreement with experiments as well as other models.

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arXiv2003

Oriented collisions for cold synthesis of superheavy nuclei

The conditions of optimum orientations (lowest barrier and largest interaction radius) for deformed colliding nuclei are introduced in "cold" fusion of superheavy nuclei. Also, the role of (octupole and) hexadecupole deformations is studied. We have used the proximity potential and applied our method to Ca-induced reactions.

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arXiv2003

Closed shell effects from the stability and instability of deformed and superdeformed nuclei against cluster decays in the mass regions 130-158 and 180-198

The stability and/or instability of the deformed and superdeformed nuclei, $^{133-137}_{60}$Nd, $^{144-158}_{64}$Gd, $^{176-194}_{80}$Hg, and $^{192-198}_{82}$Pb parents, coming from three regions of different superdeformations, are studied with respect to the $α$ and heavy cluster decays. The $α$-decay studies also include the heavier $^{199-210}$Pb nuclei, for reasons of spherical magic shells at Z=82 and N=126. The calculations are made by using the preformed cluster-decay model, and the obtained $α$-decay half-lives are compared with the available experimental data. Having met with a very good success for the comparisons of $α$-decay half-lives and in giving the associated known magic or sub-magic closed shell structures of both the parent nuclei and daughter products, the interplay of closed shell effects in the cluster-decay calculations is investigated. The cluster-decay calculations also give the closed shell effects of known spherical magicities, both for the parent and daughter nuclei, and further predict new (deformed) closed shells at Z=72-74 and N=96-104 due to both the stability and instability of Hg and Pb parents against cluster decays. Specifically, a new deformed daughter radioactivity is predicted for various cluster decays of $^{186-190}$Hg and $^{194,195}$Pb parents with the best possible measurable cases identified as the $^8$Be and $^{12}$C decays of $^{176,177}$Hg and/or $^{192}$Pb parents. The predicted decay half-lives are within the measurable limits of the present experimental methods. The interesting point to note is that the parents with measurable cluster decay rates are normal deformed nuclei at the transition between normal and super-deformation.

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arXiv2003

Emission of intermediate mass fragments from hot $^{116}$Ba$^*$ formed in low-energy $^{58}$Ni+$^{58}$Ni reaction

The complex fragments (or intermediate mass fragments) observed in the low-energy $^{58}$Ni+$^{58}$Ni$\to ^{116}$Ba$^*$ reaction, are studied within the dynamical cluster decay model for s-wave with the use of the temperature-dependent liquid drop, Coulomb and proximity energies. The important result is that, due to the temperature effects in liquid drop energy, the explicit preference for $α$-like fragments is washed out, though the $^{12}$C (or the complementary $^{104}$Sn) decay is still predicted to be one of the most probable $α$-nucleus decay for this reaction. The production rates for non-$α$ like intermediate mass fragments (IMFs) are now higher and the light particle production is shown to accompany the IMFs at all incident energies, without involving any statistical evaporation process in the model. The comparisons between the experimental data and the (s-wave) calculations for IMFs production cross sections are rather satisfactory and the contributions from other $\ell$-waves need to be added for a further improvement of these comparisons and for calculations of the total kinetic energies of fragments.

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arXiv2003

Cluster-decay of hot $^{56}$Ni$^*$ formed in $^{32}$S+$^{24}$Mg reaction

The decay of $^{56}Ni^*$, formed in $^{32}S+^{24}Mg$ reaction at the incident energies $E_{cm}$=51.6 and 60.5 MeV, is calculated as a cluster decay process within the Preformed Cluster-decay Model (PCM) of Gupta et al. re-formulated for hot compound systems. The observed deformed shapes of the exit channel fragments are simulated by introducing the neck-length parameter at the scission configuration, which nearly coincides the $^{56}Ni$ saddle configuration. This is the only parameter of the model, which though is also defined in terms of the binding energy of the hot compound system and the ground-state binding energies of the various emitted fragments. The calculated s-wave cross sections for nuclear shapes with outgoing fragments separated within nuclear proximity limit (here $\sim$0.3 fm) can be compared with the experimental data, and the TKEs are found to be in reasonably good agreement with experiments for the angular momentum effects added in the sticking limit for the moment of inertia. Also, some light particle production (other than the statistical evaporation residue, not treated here) is predicted at these energies and, interestingly, $^4He$, which belongs to evaporation residue, is found missing as a dynamical cluster-decay fragment.

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