118982481
Neutron drip line in odd and even mass calcium and nickel nuclei
Neutron-rich Ca and Ni nuclei have been studied in a spherical relativistic mean-field formalism in coordinate space. A {delta} interaction has been adopted to treat the pairing correlations for the neutrons. Odd nuclei have been treated in the blocking approximation. The effect of the positive-energy continuum and the role of pairing in the stability of nuclei have been investigated by use of the resonant-BCS approach. In Ca isotopes, N=50 is no longer a magic number, whereas in Ni nuclei, a new magic number emerges at N=70. There is a remarkable difference in the relative positions of the drip lines for odd and even isotopes. In Ca isotopes, the last bound even and odd nuclei are found to be {sup 72}Ca and {sup 59}Ca, respectively. In Ni isotopes, the corresponding nuclei are {sup 98}Ni and {sup 97}Ni, respectively. The origin of this difference in relative positions of the drip line in even and odd isotopes in the two chains is traced to the difference in the single-particle level structures and consequent modification in the magic numbers in the two elements. Pairing interaction is seen to play a major role. The effect of the width of the resonance states on pairing hasmore » also been investigated.« less
124431237
Massive neutron stars with a hyperonic core: A case study with the IUFSU relativistic effective interaction
The recent discoveries of massive neutron stars, such as PSR J0348 + 0432 and PSR J1614–2230, have raised questions about the existence of exotic matter such as hyperons in the neutron star core. The validity of many established equations of states (EoSs) like GM1 and FSUGold are also questioned. We investigate the existence of hyperonic matter in the central regions of massive neutron stars by using relativistic mean field (RMF) theory with the recently proposed Indiana University Florida State University (IUFSU) model. The IUFSU model is extended by including hyperons to study the neutron star in β equilibrium. The effect of different hyperonic
119481144
Role of pairing interaction in neutron rich odd and even Zr nuclei
Neutron rich Zr nuclei with number of neutrons between N=50 and 82 are investigated in the relativistic mean field approach in coordinate space. The resonant levels in the positive energy continuum have been explicitly included in the calculation. Odd nuclei have been treated in the blocking approximation. Our calculation indicates that the dripline for odd mass isotopes is far away from that for the even mass ones. Pairing interaction plays a significant role in stabilizing the even isotopes, thus extending the dripline for them.
123101749
Formation of Anti-Hydrogen in Presence of Laser Field in Antiproton-Positronium Collisions
A detailed calculation in the framework of first Born approximation has been presented for the study of anti-hydrogen formation in antiproton-positronium collisions in presence of a laser field considered classically in the dipole approximation. The projectile-laser field interaction and the dressing of the bound states are considered to first order. The anti-hydrogen formation amplitudes are obtained in closed forms in the Ap gauge, the field direction being parallel to the incident momentum. The differential as well as total cross-sections are presented for no photon (l = 0) and one photon (l = ±1) exchange with field strengths e0 = 106 V/cm (0.0002 a.u.) and e0 = 107 V/cm (0.002 a.u.) and compared with the corresponding field free results.
119118939
Helium nuclei around the neutron drip line
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 $^{6,8}$He and compared with experiment. The energies of the low-lying resonance states in the neutron unstable nuclei $^{5,7}$He have also been calculated and compared with experimental observations.
3205210
Correction to Relativistic Mean Field binding energy and NpNn scheme
Abstract The differences between the experimental and Relativistic Mean Field binding energies have been calculated for a large number of even–even nuclei from A = 50 to 220. Excluding certain mass regions, the differences, after suitable corrections for particular isotope chains, are found to be proportional to the Casten factor P, chosen as a measure of n – p interaction strength in a nucleus. Results for even-Z odd-N nuclei are also seen to follow the same relation, if the odd–even mass difference is taken into account following the semiempirical formula. This indicates that the n – p interaction is the major contributor to the difference between the calculated and the experimental binding energies.
121755167
Electron capture decay of In-116 and nuclear structure of double beta decays
Quasiparticle-random-phase-approximation (QRPA) calculations of double {beta} decays have not been able to reproduce data in the A=100 system. We propose the A=116 system{emdash}because of its smaller deformation{emdash}as a simpler system to test QRPA calculations. We present results of two experiments we performed, which determine the electron-capture-decay branch of {sup 116}In to be (2.27{plus_minus}0.63){times}10{sup {minus}2}{percent}, from which we deduce logft=4.39{sub {minus}0.15}{sup +0.10}. We present QRPA calculations and compare their predictions to experimental data. Finally we use these calculations to predict the 2{nu} double-{beta}-decay rate of {sup 116}Cd to the ground and excited states of {sup 116}Sn. {copyright} {ital 1998} {ital The American Physical Society}
45540139
Precise study of the final-state continua in 8 Li and 8 B decays
We studied β-delayed singles-α spectra from 8Li and 8B decays with special emphasis on a careful calibration of the energy scale. 8Li and 8B activities were produced by 7Li(d, p) and 6Li(3He,n) reactions, respectively, and deposited in thin C foils. Delayed α’s were counted in thin, cooled Si detectors with small solid angles to reduce summing with β’s. The energy scale and detector response were calibrated with spectroscopic grade radioactive sources. We extracted the 8Li and 8B final-state continuum shapes from our spectra by using R-matrix analyses that included effects of lepton-recoil broadening and detector response. Our results are in excellent agreement with a recent measurement using 8B’s implanted in a Si counter and in good agreement with our reanalysis of the older Wilkinson-Alburger 8Li and 8B data, but disagree with a recent 8B experiment using a coincidence technique.