108 research outputs found
Mirror symmetry breaking in He isotopes and their mirror nuclei
We study the mirror symmetry breaking of He-Be and He-C using
the He + N (=2, 4) cluster model. The many-body resonances are
treated for the correct boundary condition using the complex scaling method. We
find that the ground state radius of C is larger than that of He due to
the Coulomb repulsion in C. On the other hand, the resonances of
the two nuclei exhibit the inverse relation; the C radius is smaller than
the He radius. This is due to the Coulomb barrier of the valence protons
around the He cluster core in C, which breaks the mirror symmetry of
the radius in the two nuclei. A similar variation in the radius is obtained in
the mirror nuclei, He and Be. A very large spatial extension of valence
nucleons is observed in the states of He and C. This property
is related to the dominance of the configuration for
four valence nucleons, which is understood from the reduction in the strength
of the couplings to other configurations by involving the spatially extended
components of valence nucleons.Comment: 9 pages, 5 figure
Five-body resonances of 8C using the complex scaling method
We study the resonance spectroscopy of the proton-rich nucleus 8C in the
alpha+p+p+p+p cluster model. Many-body resonances are treated on the correct
boundary condition as the Gamow states using the complex scaling method. We
obtain the ground state of 8C as a five-body resonance for the first time,
which has dominantly the sub-closed (p_{3/2})^4 configuration and agrees with
the recent experiment for energy and decay width. We predict the second 0+
state with the excitation energy of 5.6 MeV, which corresponds to the
state from the ground state. We evaluate the occupation numbers of four
valence-protons in the 8C states and also the J^\pi distribution of proton-pair
numbers of the two 0+ states of 8C. The ground state involves a large amount of
the 2+ proton-pair fraction, while the excited 0+_2 state almost consists of
two of the 0+ proton pairs, which can be understood from the
(p_{3/2})^2(p_{1/2})^2 configuration. We also discuss the mirror symmetry
between 8C and 8He with an alpha+four nucleon picture. It is found that the 0+
states retain the mirror symmetry well for the configuration properties of two
nuclei.Comment: 8 pages, 6 figures. arXiv admin note: text overlap with
arXiv:1111.5070, radial properties of 8C are revised in Table II
Tensor correlation in 4He and its Effect on the doublet splitting in 5He
We investigate the role of tensor correlation on the structures of
\nuc{4}{He} and its effect on the doublet splitting in \nuc{5}{He}. We perform
a configuration mixing calculation in the shell model type bases to represent
the tensor correlation for He. It is found that our model describes the
characteristics of the tensor correlation, which is represented by an admixture
of the configuration with a spatially modified orbit. For
He, we solve a coupled OCM equation for an extended He+ model, while
taking into account the tensor correlation in the He cluster. It is shown
that the tensor correlation produces the Pauli blocking, in particular, for the
state, and its effect causes about half of the p-wave doublet
splitting in He. This indicates that the strength of the effective
spin-orbit interaction should be reduced by about half from the conventional
one. We obtain a reliable He- interaction, including the tensor
correlation, which further improves the behavior of the - and -wave phase
shifts in the He+ system.Comment: 21 pages, 9 figures, To be published in Progress of Theoretical
Physic
One-neutron removal strength of 7He into 6He using the complex scaling method
We study the one-neutron removal strength of the 7He ground state, which
provides us with the 6He-n component in 7He. The He isotopes are described on
the basis of the 4He+Xn cluster model (X=1,2,3). The complex scaling method is
applied to describe not only the Gamow resonances but also the nonresonant
continuum states of valence neutrons, with the correct boundary condition of
particle decays. The one-neutron removal strength of 7He into the unbound
states of 6He is calculated using the complex-scaled Green's function, in which
a complex-scaled complete set of 4He+n+n states is adopted. Using this
framework, we investigate resonant and nonresonant contributions of the
strength, which individually produce specific structures in the distributions.
In addition, we propose a method to obtain the real-value strength using the
complex values of spectroscopic factors of Gamow states. As a result, the
6He(2+) resonance is found to give the largest contribution.Comment: 11 pages, 10 figures, Corrected typo
Level Density in the Complex Scaling Method
It is shown that the continuum level density (CLD) at unbound energies can be
calculated with the complex scaling method (CSM), in which the energy spectra
of bound states, resonances and continuum states are obtained in terms of
basis functions. In this method, the extended completeness relation is applied
to the calculation of the Green functions, and the continuum-state part is
approximately expressed in terms of discretized complex scaled continuum
solutions. The obtained result is compared with the CLD calculated exactly from
the scattering phase shift. The discretization in the CSM is shown to give a
very good description of continuum states. We discuss how the scattering phase
shifts can inversely be calculated from the discretized CLD using a basis
function technique in the CSM.Comment: 14 pages, 9 figures, To be published in Progress of Theoretical
Physic
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