Pseudo-spin as a relativistic symmetry

The existence of broken pseudo-spin symmetry in the Pb nucleus has been studied in the relativistic mean field approach using realistic Lagrangian parameters. Its relationship to spin orbit splitting and the vanishingly small surface delta character of the mean spin orbit potential are investigated. In the ²⁰⁸Pb nucleus the broken pseudo-spin doublets are found to exist above the neutron (proton) Fermi surfaces. Received: 16 April 1998 / Revised version: 26 June 1998     

Analysis of two neutron (proton) transfer reaction data in the Zr-region

The spectroscopic amplitudes, form factors, angular distributions and total cross-sections for two nucleon transfer reactions in Zr-region in the zero range distorted wave Born approximation are calculated using consistent set of shell model wave functions. A single normalisation factor gives a good fit to all the two neutron transfer reaction data whereas the corresponding fit for the two-proton transfer reaction data is less satisfactory.     

Study of Exotic Nuclei

A high-sensitive fluorescence cell has been developed with an aim to perform laser spectroscopy of exotic nuclei. This fluorescence cell has been tested off-line for stable isotope ¹³³Cs. Also, an investigation of the nuclear root mean square (r.m.s.) charge and neutron radii, and of the binding energies of the cesium long isotopic chain has been carried out in the relativistic mean field (RMF) and relativistic Hartree–Bogoliubov (RHB) formalisms. The RMF/RHB calculations are compared with the experimental data and are found to be in good agreement.     

Preparation and characterization of poly-N-vinyl carbazole langmuir-blodgett films

Langmuir monolayers of poly-N-vinyl carbazole (PNVK) were obtained by dispensing PNVK dissolved in tetrahydrofuran onto an air-water interface. Surface pressure-area isotherms of mixed monolayer of the PNVK were studied under different subphase conditions such as temperature and pH of the subphase. It was demonstrated that the monolayer of PNVK remained stable over a temperature range of 10–40°C. The area per molecule of the solid phase was found to be 31Ų. These monolayers were transferred onto indium-tin-oxide-coated glass plates and characterized by spectroscopic and electrochemical techniques.     

Semi-phenomenological neutron density distributions

The simple algebraic form for the nuclear densities designed to incorporate correctly, the two physical requirements, namely, the asymptotic behaviour and the behaviour near the centre, is used to calculate the neutron distributions in several nuclei. Sample neutron densities for 58,64 Ni, ¹¹⁶Sn and ²⁰⁸Pb are presented. The calculation reveals an excellent agreement with the experiment as well as with the relativistic and nonrelativistic microscopic mean field calculations. The use of this algebraic form of the densities in the analytic studies is strongly advocated.     

Coimmobilization of urease and glutamate dehydrogenase in electrochemically prepared polypyrrole-polyvinyl sulfonate films

Immobilization of urease and glutamate dehydrogenase enzymes in electrochemically prepared polypyrrole-polyvinyl sulfonate films (PPY-PVS) was carried out using physical adsorption and electrochemical entrapment techniques. Detailed studies on optimum pH, Fourier transform infrared spectroscopy, cyclic voltammetry, and scanning electron microscopy of the enzymes in the immobilized state were conducted. The value of the apparent Michaelis-Menten constant was experimentally determined to be 2.5 and 2.7 for physically adsorbed and electrochemically entrapped urease in PPY-PVS films, respectively.     

Microscopic description of superheavy nuclei

The results of extensive microscopic relativistic mean field (RMF) calculations for the nuclei appearing in the α-decay chains of recently discovered superheavy elements with 109  Z  118 are presented and discussed. The calculated ground-state properties like total binding energies, Q-values, deformations, radii, and densities closely agree with the corresponding experimental data, where available. The root mean square radii closely follow A^1/3 law (A being the mass number) with the constant r_o = 0.9639 ± 0.0005 fm. The double folding (tρρ) approximation is used to calculate the interaction potential between the daughter and the α, using RMF densities along with the density-dependent nucleon–nucleon interaction (M3Y). This in turn is employed within the WKB approximation to estimate the half-lives without any additional parameter for α-decay. The half-lives are highly sensitive to the Q-values used and qualitatively agree with the corresponding experimental values. The use of experimental Q-values in the WKB approximation improves the agreement with the experiment, indicating that the resulting interaction potential is reliable and can be used with confidence as the real part of the optical potential in other scattering and reaction processes.     

Qualitative features of Pauli break-up from the configuration space viewpoint

A dimensionless measure of the effect of Pauli exclusion upon the neutron-proton interaction in a projectile deuteron is calculated in the zero range approximation for a Hulthen deuteron. One learns thereby that the Pauli break-up matrix element is distributed differently in space from that for nuclear break-up and that the effect with decreasing energy to a large value at the lowest deuteron energies.