G. Gangopadhyay

Microscopic calculation of half lives of spherical proton emitters

Abstract Half life values for proton radioactivity in nuclei have been calculated in the WKB approximation. The microscopic proton–nucleus potential has been obtained by folding the densities of daughter nuclei with two microscopic NN interactions, DDM3Y and JLM. The densities have been obtained in the Relativistic Mean Field approach in the spherical approximation using the force FSU Gold. No substantial modification of results has been observed if other common forces are employed. The calculated results for the decays from the ground state or the low-lying excited states in almost all the nuclei agree well with experimental measurements. Reasons for large deviations in a few cases have been discussed. Results in 109 I and 112,113 Cs show that the effect of deformation is small contrary to earlier calculations. Predictions for possible proton radioactivity have been made in two nuclei, 93 Ag and 97 In.

Cluster decay in very heavy nuclei in a relativistic mean field model

Exotic cluster decay of very heavy nuclei was studied in the microscopic Super-Asymmetric Fission Model. The Relativistic Mean Field model with the force FSU Gold was employed to obtain the densities of the cluster and the daughter nuclei. The microscopic nuclear interaction DDM3Y1, which has an exponential density dependence, and the Coulomb interaction were used in the double folding model to obtain the potential between the cluster and the daughter. Half-life values were calculated in the WKB approximation and the spectroscopic factors were extracted. The latter values are seen to have a simple dependence of the mass of the cluster as has been observed earlier. Predictions were made for some possible decays.

α-decay lifetime in superheavy nuclei with A > 282

Nuclei with

Simple parametrization of an α-decay spectroscopic factor in the 150 ⩽ A ⩽ 200 region

Ag282

A NEW PHENOMENOLOGICAL FORMULA FOR GROUND-STATE BINDING ENERGIES

have been studied in the relativistic mean field approach using the force FSU Gold and a zero range pairing interaction. The Euler-Lagrange equations have been solved in the coordinate space. The \ensuremath{\alpha}-nucleus potential has been constructed with the density-dependent M3Y interaction (DDM3Y1), which has an exponential density dependence, in the double folding model using the nucleon densities in the daughter nucleus and the \ensuremath{\alpha} particle. Half-lives of \ensuremath{\alpha} decay have been calculated for tunneling of the \ensuremath{\alpha} particle through the potential barrier in the WKB approximation and assuming a constant preformation probability. The resulting values agree well with experimental measurements.

Microscopic calculation of proton capture reactions in the mass 60–80 region and its astrophysical implications

Half-life values for α-decay in the mass region A = 150–200 have been calculated in the microscopic super asymmetric fission model. The interaction between the α-particle and the daughter nucleus has been obtained in the double folding model with the microscopic interaction DDM3Y1. Theoretical densities for the nuclei involved have been calculated in the relativistic mean-field approach with the Lagrangian density FSU Gold. Spectroscopic factors for α-decay, calculated as the ratios of the theoretically calculated and experimentally measured half-life values, show a simple dependence on the mass number and the product of the number of valence protons and neutrons. The implications of the parametrization have been discussed. Finally, based on this simple relation, α-decay half-life values in a number of nuclei have been predicted.

Spectroscopic factors for alpha decay in the N(p)N(n) scheme

A phenomenological formula based on liquid drop model has been proposed for ground-state binding energies of nuclei. The effect due to bunching of single particle levels has been incorporated through a term resembling the one-body Hamiltonian. The effect of n–p interaction has been included through a function of valence nucleons. A total of 50 parameters has been used in the present calculation. The root mean square (r.m.s.) deviation for the binding energy values for 2140 nuclei comes out to be 0.376 MeV, and that for 1091 alpha decay energies is 0.284 MeV. The correspondence with the conventional liquid drop model is discussed.

Helium nuclei around the neutron drip line

Microscopic optical potentials obtained by folding the DDM3Y interaction with the densities from the Relativistic Mean-Field approach have been utilized to evaluate S-factors of low-energy (p, γ) reactions in the mass 60–80 region and to compare with experiments. The Lagrangian density FSU Gold has been employed. Astrophysical rates for important proton capture reactions have been calculated to study the behaviour of rapid proton nucleosynthesis for waiting point nuclei with mass less than A = 80.

Valence particles and the correction to relativistic mean field binding energy

Abstract Lifetime values for alpha decay in even–even nuclei with Z = 84 – 98 and N = 128 – 152 have been calculated in the superasymmetric fission model. The interaction between the alpha particle and the daughter nucleus has been formed in the double folding approach using a density dependent NN interaction. The densities have been obtained using the Relativistic Mean Field formalism. The spectroscopic factors for the decays have been deduced and are shown to vary smoothly as a function of effective numbers of valence nucleons, N p and N n chosen with a suitable core. The implication of such a smooth behaviour has been discussed.

Rotational bands in the doubly odd 138Pm

Neutron rich He nuclei have been investigated using relativistic mean field approach in co-ordinate space. Elastic partial scattering cross sections for proton scattering in inverse kinematics have been calculated using the theoretically obtained density for