315 research outputs found
Description of two-electron atoms with correct cusp conditions
New sets of functions with arbitrary large finite cardinality are constructed
for two-electron atoms. Functions from these sets exactly satisfy the Kato's
cusp conditions. The new functions are special linear combinations of
Hylleraas- and/or Kinoshita-type terms. Standard variational calculation,
leading to matrix eigenvalue problem, can be carried out to calculate the
energies of the system. There is no need for optimization with constraints to
satisfy the cusp conditions. In the numerical examples the ground state energy
of the He atom is considered
Neutron Removal from the Deformed Halo 31Ne Nucleus
Experimental data on Coulomb breakup and neutron removal indicate that 31Ne
is one of the heaviest halo nuclei discovered so far. The possible ground state
of 31Ne is either 3/2- coming from p-wave halo or 1/2+ from s-wave halo. In
this work, we develop a treatable model to include deformed wave functions and
a dynamical knockout formalism which includes the dependence on the nuclear
orientation to study the neutron removal from 31Ne projectiles at energies
around E=200 MeV/nucleon. A detailed account of the effects of deformation on
cross sections and longitudinal momentum distributions is made. Our numerical
analysis indicates a preference for the 31Ne ground state with spin parity
3/2-.Comment: 22 pages, 13 figures, accepted for publication in the Physical Review
Shadow poles in a coupled-channel problem calculated with Berggren basis
In coupled-channel models the poles of the scattering S-matrix are located on
different Riemann sheets. Physical observables are affected mainly by poles
closest to the physical region but sometimes shadow poles have considerable
effect, too. The purpose of this paper is to show that in coupled-channel
problem all poles of the S-matrix can be calculated with properly constructed
complex-energy basis. The Berggren basis is used for expanding the
coupled-channel solutions. The location of the poles of the S-matrix were
calculated and compared with an exactly solvable coupled-channel problem: the
one with the Cox potential. We show that with appropriately chosen Berggren
basis poles of the S-matrix including the shadow ones can be determined.Comment: 11 pages, 4 figures, 59 reference
Radiative nucleon capture with quasi-separable potentials
We study radiative capture reactions using quasi-separable potentials. This
procedure allows an easier treatment of non-local effects that can be extended
to three-body problems. Using this technique, we calculate the neutron and
proton radiative capture cross sections on C. The results obtained are
shown to be in good agreement with the available experimental data.Comment: 12 pages, 4 figures, accepted for publication in Journal of Physics
G: Nuclear and Particle Physic
Nuclear three-body problem in the complex energy plane: Complex-Scaling-Slater method
The physics of open quantum systems is an interdisciplinary area of research.
The nuclear "openness" manifests itself through the presence of the many-body
continuum representing various decay, scattering, and reaction channels. As the
radioactive nuclear beam experimentation extends the known nuclear landscape
towards the particle drip lines, the coupling to the continuum space becomes
exceedingly more important. Of particular interest are weakly bound and unbound
nuclear states appearing around particle thresholds. Theories of such nuclei
must take into account their open quantum nature. To describe open quantum
systems, we introduce a Complex Scaling (CS) approach in the Slater basis. We
benchmark it with the complex-energy Gamow Shell Model (GSM) by studying
energies and wave functions of the bound and unbound states of the two-neutron
halo nucleus 6He viewed as an + n + n cluster system. In the CS
approach, we use the Slater basis, which exhibits the correct asymptotic
behavior at large distances. To extract particle densities from the
back-rotated CS solutions, we apply the Tikhonov regularization procedure,
which minimizes the ultraviolet numerical noise. While standard applications of
the inverse complex transformation to the complex-rotated solution provide
unstable results, the stabilization method fully reproduces the GSM benchmark.
We also propose a method to determine the smoothing parameter of the Tikhonov
regularization. The combined suite of CS-Slater and GSM techniques has many
attractive features when applied to nuclear problems involving weakly-bound and
unbound states. While both methods can describe energies, total widths, and
wave functions of nuclear states, the CS-Slater method, if it can be applied,
can provide an additional information about partial energy widths associated
with individual thresholds.Comment: 15 pages, 16 figure
Curvature Correction in the Strutinsky's Method
Mass calculations carried out by Strutinsky's shell correction method are
based on the notion of smooth single particle level density. The smoothing
procedure is always performed using curvature correction. In the presence of
curvature correction a smooth function remains unchanged if smoothing is
applied. Two new curvature correction methods are introduced. The performance
of the standard and new methods are investigated using harmonic oscillator and
realistic potentials.Comment: 4 figures, submitted to Journal of Physics G: Nuclear and Particle
Physic
Shell corrections for finite depth potentials: Particle continuum effects
Shell corrections of finite, spherical, one-body potentials are analyzed
using a smoothing procedure which properly accounts for the contribution from
the particle continuum, i.e., unbound states. Since the plateau condition for
the smoothed single-particle energy seldom holds, a new recipe is suggested for
the definition of the shell correction. The generalized Strutinsky smoothing
procedure is compared with the results of the semi-classical Wigner-Kirkwood
expansion. A good agreement has been found for weakly bound nuclei in the
vicinity of the proton drip line. However, some deviations remain for extremely
neutron-rich systems due to the pathological behavior of the semi-classical
level density around the particle threshold.Comment: 18 pages, 8 figure
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