P. Roy Chowdhury

α decay half-lives of new superheavy elements

The lifetimes of \ensuremath{\alpha} decays of the recently produced isotopes of elements 112, 114, 116, and

Predictions of alpha decay half lives of heavy and superheavy elements

{}^{294}118

MODIFIED BETHE–WEIZSÄCKER MASS FORMULA WITH ISOTONIC SHIFT AND NEW DRIPLINES

and of some decay products are calculated theoretically within the WKB approximation by use of microscopic \ensuremath{\alpha}-nucleus interaction potentials. We obtain these nuclear potentials by folding the densities of the \ensuremath{\alpha} and the daughter nuclei with the M3Y effective interaction, supplemented by a zero-range pseudopotential for exchange along with the density dependence. Spherical charge distributions are used for calculating the Coulomb interaction potentials. These calculations provide reasonable estimates for the observed \ensuremath{\alpha} decay lifetimes and thus provide reliable predictions for other superheavies.

Folding model analysis of proton radioactivity of spherical proton emitters

Abstract Theoretical estimates for the lifetimes of several isotopes of heavy elements with Z = 102 – 120 are presented by calculating the quantum mechanical tunneling probability in a WKB framework and using microscopic nucleus–nucleus potential obtained by folding the densities of interacting nuclei with the DDM3Y effective nuclear interaction. The α -decay half lives calculated in this formalism using the experimental Q -values are in good agreement over a wide range of experimental data. Half lives are also calculated using Q -values extracted from two mass formulae. The Viola–Seaborg–Sobiczewski (VSS) estimates of α -decay half lives with the same Q -values are presented for comparison. The half life calculations are found to be quite sensitive to the choice of Q -values. Comparison with the experimental data delineates the inadequacies of older mass predictions in the domain of heavy and superheavy elements as compared to the newer one by Muntian–Hofmann–Patyk–Sobiczewski, and highlights necessity of a more accurate mass formula which can predict Q -values with even higher precision.

Fusion ofLi6withTb159at near-barrier energies

Nuclear masses are calculated using the modified Bethe–Weizsacker mass formula in which the isotonic shifts have been incorporated. The results are compared with the improved liquid drop model with isotonic shift. Mass excesses predicted by this method compares well with the microscopic–macroscopic model while being much more simple. The neutron and proton drip lines have been predicted using this modified Bethe–Weizsacker mass formula with isotonic shifts.

Nuclear equation of state at high baryonic density and compact star constraints

Half-lives of the decays of spherical nuclei away from the proton drip line by proton emissions are estimated theoretically. The quantum mechanical tunneling probability is calculated within the WKB approximation. Microscopic proton-nucleus interaction potentials are obtained by single folding the densities of the daughter nuclei with M3Y effective interaction supplemented by a zero-range pseudopotential for exchange along with the density dependence. Parameters of the density dependence are obtained from the nuclear matter calculations. Spherical charge distributions are used for Coulomb interaction potentials. These calculations provide reasonable estimates for the observed proton-radioactivity lifetimes of proton-rich nuclei for proton emissions from 26 ground and isomeric states of spherical proton emitters.

α decay chains from element 113

Complete and incomplete fusion cross sections for {sup 6}Li + {sup 159}Tb have been measured at energies around the Coulomb barrier by the {gamma}-ray method. The measurements show that the complete fusion cross sections at above-barrier energies are suppressed by {approx}34% compared to coupled-channel calculations. A comparison of the complete fusion cross sections at above-barrier energies with the existing data for {sup 11,10}B + {sup 159}Tb and {sup 7}Li + {sup 159}Tb shows that the extent of suppression is correlated with the {alpha} separation energies of the projectiles. It has been argued that the Dy isotopes produced in the reaction {sup 6}Li + {sup 159}Tb at below-barrier energies are primarily due to the d transfer to unbound states of {sup 159}Tb, while both transfer and incomplete fusion processes contribute at above-barrier energies.

Lambda hyperonic effect on the normal drip lines

Abstract A mean field calculation is carried out to obtain the equation of state (EoS) of nuclear matter from a density-dependent M3Y interaction (DDM3Y). The energy per nucleon is minimized to obtain ground state of the symmetric nuclear matter (SNM). The constants of density dependence of the effective interaction are obtained by reproducing the saturation energy per nucleon and the saturation density of SNM. The energy variation of the exchange potential is treated properly in the negative energy domain of nuclear matter. The EoS of SNM, thus obtained, is not only free from the superluminosity problem but also provides excellent estimate of nuclear incompressibility. The EoS of asymmetric nuclear matter is calculated by adding to the isoscalar part, the isovector component of M3Y interaction. The SNM and pure neutron matter EoS are used to calculate the nuclear symmetry energy which is found to be consistent with that extracted from the isospin diffusion in heavy-ion collisions at intermediate energies. The β equilibrium proton fraction calculated from the symmetry energy and related theoretical findings are consistent with the constraints derived from the observations on compact stars.

Isobaric incompressibility of isospin asymmetric nuclear matter

Theoretical estimates of {alpha}-decay half-lives of several nuclei in the decay from element 113 are presented. Calculations in a WKB framework using DDM3Y interaction and experimental Q-values are in good agreement with the experimental data. Half-life calculations are found to be quite sensitive to the Q-values and angular momentum transfers. Calculated decay lifetime decreases, owing to more penetrability as well as thinner barrier, as Q-value increases. Deviations to this predominant behavior observed in some recent experimental data may be attributed to nonzero spin-parities in some cases.

Isospin dependent properties of asymmetric nuclear matter

A generalized mass formula is used to calculate the neutron and proton drip lines of normal and lambda hypernuclei treating non-strange and strange nuclei on the same footing. Calculations suggest the existence of several bound hypernuclei whose normal cores are unbound. Addition of Λ or ΛΛ hyperon(s) to a normal nucleus is found to cause non-uniform shifts of the neutron and proton drip lines from their conventional limits making existance of a few exotic hypernuclei beyond the normal drip lines possible.