Kazuhito Mizuyama

Di-neutron correlation and soft dipole excitation in medium mass neutron-rich nuclei near drip line

The neutron pairing correlation and the soft dipole excitation in medium mass nuclei near the drip line are investigated from the viewpoint of the di-neutron correlation. Numerical analyses based on the coordinate-space Hartree-Fock-Bogoliubov method and the continuum quasiparticle random phase approximation are performed for even-even {sup 18-24}O,{sup 50-58}Ca, and {sup 80-86}Ni. A clear signature of the di-neutron correlation is found in the ground state; two neutrons are correlated at short relative distances < or approx. 2 fm with large probability {approx}50%. The soft dipole excitation is influenced strongly by the neutron pairing correlation, and it accompanies a large transition density for pair motion of neutrons. This behavior originates from a coherent superposition of two-quasiparticle configurations [lx(l+1)]{sub L=1} consisting of continuum states with high orbital angular momenta l reaching an order of l{approx}10. It suggests that the soft dipole excitation under the influence of neutron pairing is characterized by the motion of di-neutron in the nuclear exterior against the remaining A-2 subsystem. Sensitivity to the density dependence of the effective pair force is discussed.

Dependence of single-particle energies on coupling constants of the nuclear energy density functional

We show that single-particle energies in doubly magic nuclei depend almost linearly on the coupling constants of the nuclear energy density functional. Therefore, they can be very well characterized by the linear regression coefficients, which we calculate for the coupling constants of the standard Skyrme functional. We then use these regression coefficients to refit the coupling constants to experimental values of single-particle energies. We show that the obtained rms deviations from experimental data are still quite large, of the order of 1.1 MeV. This suggests that the current standard form of the Skyrme functional cannot ensure spectroscopic-quality description of single-particle energies, and that extensions of this form are very much required.

Self-consistent microscopic description of neutron scattering by16O based on the continuum particle-vibration coupling method

The microscopic description of neutron scattering by

Linear response strength functions with iterative Arnoldi diagonalization

^{16}

RPA calculations with Gaussian expansion method

O below 30 MeV is carried out by means of the continuum particle-vibration coupling (cPVC) method with the Skyrme nucleon-nucleon (

Continuum particle-vibration coupling method in coordinate-space representation for finite nuclei

NN

Continuum quasiparticle linear response theory using the Skyrme functional for multipole responses of exotic nuclei

) effective interaction. In the cPVC method, a proper boundary condition on a nucleon in continuum states is imposed, which enables one to evaluate the transition matrix in a straightforward manner. Experimental data of the total and total-elastic cross sections are reproduced quite well by the cPVC method. An important feature of the result is the fragmentation of the single-particle resonance into many peaks as well as the shift of its centroid energy. Thus, some part of the fine structure of the experimental cross sections at lower energies is well described by the cPVC framework. The cPVC method based on a real

Pairing collectivity in medium-mass neutron-rich nuclei near drip-line

NN

Correction of the thermal neutron capture cross section of 241Am obtained by the Westcott convention

effective interaction is found to successfully explain about 85% of the reaction cross section, through explicit channel-coupling effects.

Subtraction of the spurious translational mode from the random-phase approximation response function

We report on an implementation of a new method to calculate random phase approximation (RPA) strength functions with iterative non-Hermitian Arnoldi diagonalization method, which does not explicitly calculate and store the RPA matrix. We discuss the treatment of spurious modes, numerical stability, and how the method scales as the used model space is enlarged. We perform the particle-hole RPA benchmark calculations for double magic nucleus