Single-particle Quadrupole Research Articles

The effect of core polarization on longitudinal form factors in 10B

Electron scattering Coulomb form factors for the single-particle quadrupole transitions in the p-shell 10B nucleus have been studied. Core polarization effects are included through a microscopic theory that includes excitations from the core orbits up to higher orbits with 2ℏω excitations. The modified surface delta interaction is employed as a residual interaction. The effect of core polarization is found essential in both the transition strengths and momentum transfer dependence of form factors, and gives remarkably good agreement with the measured data with no adjustable parameters.

Single-particle quadrupole electromagnetic transitions in p-shell and sd-shell nuclei

Electron scattering Coulomb form factors for the single-particle quadrupole transitions in p-shell and sd-shell nuclei have been studied. Core polarization effects are included through a microscopic theory that includes excitations from the core orbits up to higher orbits with 2ω excitations. The modified surface delta interaction is adopted as a residual interaction. The results are discussed for the ( 1p1/2-1↦1p3/2-1) proton transition in 15N, ( 1d5/2↦2s1/2) neutron transition in 17O and ( 1d3/2-1↦2s1/2-1) proton transition in 39K. The inclusion of core polarization effects modifies the form factors markedly and describes the experimental data very well in both the absolute strength and the momentum transfer dependence.

Quadrupole moments of highly deformed structures in the A approximately 135 region: probing the single-particle motion in a rotating potential.

The latest generation gamma-ray detection system, GAMMASPHERE, coupled with the Microball charged-particle detector, has made possible a new class of nuclear lifetime measurement. For the first time differential lifetime measurements free from common systematic errors for over 15 different nuclei ( >30 rotational bands in various isotopes of Ce, Pr, Nd, Pm, and Sm) have been extracted at high spin within a single experiment. This comprehensive study establishes the effective single-particle transition quadrupole moments in the A approximately 135 light rare-earth region. Detailed comparisons are made with theoretical calculations using the self-consistent cranked mean-field theory which convincingly demonstrates the validity of the additivity of single-particle quadrupole moments in this mass region.

Polarization effects in superdeformed nuclei

A detailed theoretical investigation of polarization effects in superdeformed nuclei is performed. In the pure harmonic oscillator potential it is shown that when one particle (or hole) with the mass single-particle quadrupole moment q ν is added to a superdeformed core, the change of the electric quadrupole moment can be parameterized as q eff = e( bq ν + a), and analytical expressions are derived for the two parameters a and b. Simple numerical expressions for q eff( q ν ) are obtained in the more realistic modified oscillator model. It is also shown that quadrupole moments of nuclei with up to 10 paricles removed from the superdeformed core of 152Dy can be well described by simply subtracting effective quadrupole moments of the active single-particle states from the quadrupole moment of the core. Tools are given for estimating the quadrupole moment for possible configurations in the superdeformed A ∼ 150 region.

Single-particle calculations in an axially deformed Woods-Saxon potential with Cassinian ovals parametrization of the shape deformation

Single-particle energies and wave functions of an axially deformed Woods-Saxon potential are computed. The nuclear shape may be defined in terms of an expansion into spherical harmonics or in terms of Cassinian oval parameterization. The standard liquid drop model constants, effective barriers for the unbound states, single-particle quadrupole moments and g-factors are also calculated. The applied shape parameterization of the potential well allows to generate the single particle orbitals also for the extreme deformations, even for two-centre-type problems.

Single-particle energies, wave functions, quadrupole moments and g-factors in an axially deformed woods-saxon potential with applications to the two-centre-type nuclear problems

Single-particle energies and wave functions of an axially deformed Woods-Saxon potential are computed. The Hamiltonian used includes the spin-orbit interaction and the Coulomb potential for protons. The nuclear shape is defined in terms of an expansion into spherical-harmonics. The standard liquid-drop model constants, effective barriers for the unbound states, single-particle quadrupole moments and g-factors are also calculated. The applied shape parametrisation of the potential well allows to generate the single-particle orbitals also for the extreme deformations, e.g. those approaching separation of a nucleus into fragments, with or without the so-called mass asymmetry.

Large deformations and dissipation in a random-matrix model approach

Abstract The description of a nuclear system (one nucleus fissionning or two colliding nuclei at the time of contact) undergoing large deformations and heating-up is formulated in terms of a random-matrix model for intrinsic excitations. The choice of collective coordinates is discussed for a one-dimensional geometry, and comprises the single-particle quadrupole and octopole moments in the c.m. system. This choice is compatible with the Pauli principle and has some technical advantages. The changing representation is identified with a generalized mean field. A non-linear transport equation for the many-body density matrix is derived. This equation and related subsidiary equations describe the flow of probability flux in phase space between collective and intrinsic degrees of freedom.