Asymptotics of neutron Cooper pair in weakly bound nuclei

Asymptotic form of neutron Cooper pair penetrating to the exterior of nuclear surface is investigated with the Bogoliubov theory for the superfluid Fermions. Based on a two-particle Schr\"{o}dinger equation governing the Cooper pair wave function and systematic studies for both weakly bound and stable nuclei, the Cooper pair is shown to be spatially correlated even in the asymptotic large distance limit, and the penetration length of the pair condensate is revealed to be universally governed by the two-neutron separation energy $S_{2n}$ and the di-neutron mass $2m$

Adiabatic Selfconsistent Collective Coordinate Method for Large Amplitude Collective Motion in Superconducting Nuclei

An adiabatic approximation to the selfconsistent collective coordinate method is formulated in order to describe large amplitude collective motions in superconducting nuclei on the basis of the time-dependent Hartree-Fock-Bogoliubov equations of motion. The basic equations are presented in a local harmonic form which can be solved in a similar way as the quasiparticle RPA equations. The formalism guarantees the conservation of nucleon number expectation values. An extension to the multi-dimensional case is also discussed

Pair correlation of giant halo nuclei in continuum Skyrme-Hartree-Fock-Bogoliubov theory

The giant halos predicted in neutron-rich Zr isotopes with $A=124-138$ are investigated by using the self-consistent continuum Skyrme Hartree-Fock-Bogoliubov approach, in which the asymptotic behavior of continuum quasiparticle states is properly treated by the Green's function method. We study in detail the neutron pair correlation involved in the giant halo by analyzing the asymptotic exponential tail of the neutron pair condensate (pair density) in addition to that of the neutron particle density. The neutron quasiparticle spectra associated with these giant halo nuclei are examined. It is found that the asymptotic exponential tail of the neutron pair condensate is dominated by non-resonant continuum quasiparticle states corresponding to the scattering states with low asymptotic kinetic energy. This is in contrast to the asymptotic tail of the neutron density, whose main contributions arise from the resonant quasiparticle states corresponding to the weakly-bound single-particle orbits and resonance orbits in the Hartree-Fock potential

Collective Paths Connecting the Oblate and Prolate Shapes in 68Se and 72Kr Suggested by the Adiabatic Self-Consistent Collective Coordinate Method

By means of the adiabatic self-consistent collective coordinate method and the pairing-plus-quadrupole interaction, we have obtained the self-consistent collective path connecting the oblate and prolate local minima in 68Se and 72Kr for the first time. The self-consistent collective path is found to run approximately along the valley connecting the oblate and prolate local minima in the collective potential energy landscape. This result of calculation clearly indicates the importance of triaxial deformation dynamics in oblate-prolate shape coexistence phenomena.Comment: 24 pages including 5 figure

Application of the Adiabatic Selfconsistent-Collective-Coordinate Method to a Solvable Model of Prolate-Oblate Shape Coexistence

The adiabatic selfconsistent collective coordinate method is applied to an exactly solvable multi-O(4) model which simulates nuclear shape coexistence phenomena. Collective mass and dynamics of large amplitude collective motions in this model system are analysed, and it is shown that the method can well describe the tunneling motions through the barrier between the prolate and oblate local minima in the collective potential. Emergence of the doublet pattern is well reproduced.Comment: 25 pages including 9 figure

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 drip-line are investigated from a viewpoint of the di-neutron correlation. Numerical analyses by means of the coordinate-space HFB and the continuum QRPA methods are performed for even-even $^{18-24}$O, $^{50-58}$Ca and $^{80-86}$Ni. A clear signature of the di-neutron correlation is found in the HFB ground state; two neutrons are correlated at short relative distances \lesim 2 fm with large probability $\sim 50$. 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 $[l\times (l+1)]_{L=1}$ consisting of continuum states with high orbital angular momenta $l$ reaching an order of $l\sim 10$. It raises a picture that the soft dipole excitation under the influence of neutron pairing is characterized by motion of di-neutron in the nuclear exterior against the remaining $A-2$ subsystem. Sensitivity to the density dependence of effective pair force is discussed.Comment: 35 pages, 22 figure