Double Shell Closure Research Articles

Nuclear moments: An effective probe of nuclear stucture

Magnetic dipole and electric quadrupole moments are discussed in nuclei near doubly-closed shell nuclei (the T1 nuclei) and in nuclei along series of single-closed shell nuclei (plus of minus a few nucleons) (the In odd-mass and odd-odd nuclei). We discuss the “additivity” rules for nuclear moments. We also address the EO moment: the liquid drop model and the shell-model are discussed and compared to measurements of nuclear radii in the Ca, Sn and Pb region. In the latter region, the importance of intruder states across the Z=82 proton closed shell is emphasized.

Shell effects in Pb(p,xn) preequilibrium neutron emission.

The $^{204}$,206,207,208Pb(p,xn) reactions have been investigated at ${E}_{\mathrm{p}}$=25.5 MeV. The hard energy spectra and the structures observed in the preequilibrium continuum are attributed to the nearby double shell closure. Application of semiclassical preequilibrium models requires the reduction of the state density g and/or the use of (1p)(1n${)}^{\mathrm{\ensuremath{-}}1}$ state densities based on realistic single particle level schemes.

Influence of 2p-2h ground state correlations on charge distributions of doubly-closed shell nuclei

Ground state 2p-2h correlations are explicitly calculated in a completely self-consistent way within the framework of the Tamm-Dancoff approximation using a "universal" effective nucleon-nucleon interaction of the Skyrme type. Their influence on the charge distributions of $^{16}\mathrm{O}$, $^{40}\mathrm{Ca}$, and $^{48}\mathrm{Ca}$ is studied.NUCLEAR STRUCTURE $^{16}\mathrm{O}$, $^{40,48}\mathrm{Ca}$; ground state correlations; charge distributions; use of self-consistent methods.

Investigation of radiative pion capture in 16O by the continuum shell model

Abstract The radiative pion capture in 16O with excitation of the states above the threshold of particle emission is investigated by the continuum shell model. For simplicity, the ground state of 16O is assumed to be the double-closed shell, while the states with T = 1 are assumed to be 1p-1h configurations. The calculated widths of the strongly excited resonances (1−, 2−) agree with the experimental data. Beyond the excitation energy of 30 MeV, the photon spectra are dominated by the even parity states. The quasi-free emission of nucleons, in addition to resonances, are well reproduced.

Properties of nuclear matter andN=Z closed-shell nuclei

A simple three-parameter density dependent effective interaction is used to study the properties of nuclear matter, neutron matter and some bulk properties such as ground state energies and rms charge radii of three double-closed shell nuclei4He,16O and40Ca. The three parameters of the effective interaction are determined by requiring to fit the binding energy and density of infinite nuclear matter at saturation density as well as ground state energy of16O in the first order perturbation theory. This interaction gives correct saturation in nuclear matter with a value of 283 MeV for compressibility. The symmetry coefficientaT atkF=1·36 fm−1 is 28·58 MeV. The energy per particle in neutron matter is calculated in the range of nuclear matter densities and it compares well with those ofNemeth andSprung. Groundstate energies and rms charge radii of4He,16O and40Ca are calculated using oscillator eigen functions as single particle wave functions. Results for ground state energies are in good agreement with empirical values and rms charge radii are slightly better than those obtained byMoszkowski with the MDI.

Giant Monopole State in the Double-Closed Shell Nucleus with Excess Neutrons

approximation with good isospin basis. All 1p-1h excitation states of 2hw jump are taken in our configuration. The coupling constants of isoscalar and isovector monopole-monopole interactions are determined by the self-consistent field method. Our results show fine agree­ ment with experimental data obtained by electron and nucleon inelastic scatterings. The effects of monopole core polarization on isospin mixing and isotope shift are also discussed.

Nuclear structure of the heavyN=82 isotones:144Sm and146Gd

For single-closed shell nuclei with a large number of extra-protons, outside theZ=50,N=82 double-closed shell nucleus, a standard shell-model calculation yields dimensions of the Hamiltonian matrices beyond the scope of present computer technology. A quasi-particle (QP) calculation however, is able to describe the most important proton-excitations in a much restricted configuration space. Extended BCS+TDA calculations are performed on the single-closed shell144Sm and146Gd nuclei with a Gaussian force as effective two-body interaction. The influence of the nonconservation of the exact number of extra-protons in the BCS-approach is studied by performing a projection onto the states with an exact number of extra-protons (BCS+P). The first excited 2+, 4+ and 6+ states in146Gd are described mainly by the (1g7/2) 0 8 (2d5/2) 0 4 \((1h11/2)_{J^\pi }^2 \) configuration.

Nuclear g-factor of the 3.2 MeV 5 − state in the double-closed shell nucleus 208Pb

Nuclear g-factor of the 3.2 MeV 5 − state in the double-closed shell nucleus 208Pb

Energy Levels of Polonium-210

The energy levels of ${\mathrm{Po}}^{210}$ have been studied as populated by the electron-capture decay of ${\mathrm{At}}^{210}$. An experimental level scheme has been constructed by using data obtained from conversion electron and gamma-ray measurements made with beta-ray and scintillation spectrometers and coincidence counting techniques. A theory of the energy levels of ${\mathrm{Po}}^{210}$ has been developed using the method of Pryce to predict the levels of a nucleus containing two odd protons beyond the double-closed shell from the experimentally known levels of ${\mathrm{Bi}}^{209}$, the nucleus containing a single odd proton beyond the closed shell. Certain features of the theoretically predicted level scheme and the experimental level scheme show reasonable agreement. The spin assignment for ${\mathrm{At}}^{210}$ has been discussed with respect to the $log\mathrm{ft}$ values for its electron capture decay.