35 research outputs found
Coupled-channel continuum eigenchannel basis
The goal of this paper is to calculate bound, resonant and scattering states
in the coupled-channel formalism without relying on the boundary conditions at
large distances. The coupled-channel solution is expanded in eigenchannel bases
i.e. in eigenfunctions of diagonal Hamiltonians. Each eigenchannel basis may
include discrete and discretized continuum (real or complex energy) single
particle states. The coupled-channel solutions are computed through
diagonalization in these bases. The method is applied to a few two-channels
problems. The exact bound spectrum of the Poeschl-Teller potential is well
described by using a basis of real energy continuum states. For deuteron
described by Reid potential, the experimental energy and the S and D contents
of the wave function are reproduced in the asymptotic limit of the cutoff
energy. For the Noro-Taylor potential resonant state energy is well reproduced
by using the complex energy Berggren basis. It is found that the expansion of
the coupled-channel wave function in these eigenchannel bases require less
computational efforts than the use of any other basis. The solutions are stable
and converge as the cutoff energy increases.Comment: Accepted to be published in Physics Letters
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
Description of the proton and neutron radiative capture reactions in the Gamow shell model
We formulate the Gamow shell model (GSM) in coupled-channel (CC)
representation for the description of proton/neutron radiative capture
reactions and present the first application of this new formalism for the
calculation of cross-sections in mirror reactions 7Be(p,gamma)8B and
7Li(n,gamma)8Li. The GSM-CC formalism is applied to a translationally-invariant
Hamiltonian with an effective finite-range two-body interaction. Reactions
channels are built by GSM wave functions for the ground state 3/2- and the
first excited state 1/2- of 7Be/7Li and the proton/neutron wave function
expanded in different partial waves
Gamow shell model description of radiative capture reactions LiBe and LiLi
According to standard stellar evolution, lithium abundance is believed to be
a useful indicator of the stellar age. However, many evolved stars like red
giants show huge fluctuations around expected theoretical abundances that are
not yet fully understood. The better knowledge of nuclear reactions that
contribute to the creation and destruction of lithium can help to solve this
puzzle. In this work we apply the Gamow shell model (GSM) formulated in the
coupled-channel representation (GSM-CC) to investigate the mirror radiative
capture reactions LiBe and LiLi. The
cross-sections are calculated using a translationally invariant Hamiltonian
with the finite-range interaction which is adjusted to reproduce spectra,
binding energies and one-nucleon separation energies in Li, Be. All
relevant , , and transitions from the initial continuum states to
the final bound states and of Li and Be are
included. We demonstrate that the -wave radiative capture of proton
(neutron) to the first excited state of Be (Li) is
crucial and increases the total astrophysical -factor by about 40 \%.Comment: arXiv admin note: text overlap with arXiv:1502.0163
EFECTO DE LA RENORMALIZACIÓN DEL FACTOR ESPECTROSCÓPICO EN EL DECAMIENTO DEL 212Po
In the present work, we use the complex-energy shell model formalism to describe the alpha decay of the212Po nucleus. Single-particle bases constructed from Woods-Saxon potentials are used to build many-body basis. Spin-isospinGaussian effective interaction between all pairs of nucleons is considered. Four-body spectroscopic factor and single-particle width are calculated. The stability of the spectroscopic factor renormalization protocol is demonstrated, thus ensuring its physical significance, and its influence on the calculated alpha decay is presented. It is observed that the renormalization modifies the calculated half-life by∼40 %, which is a value three times larger than the experimental. Still, without appealing to any cluster structure from the beginning, i.e., all calculations were carried out using single nucleon degree of freedom
Gamow Shell Model description of Li isotopes and their mirror partners
Background: Weakly bound and unbound nuclei close to particle drip lines are
laboratories of new nuclear structure physics at the extremes of neutron/proton
excess. The comprehensive description of these systems requires an open quantum
system framework that is capable of treating resonant and nonresonant many-body
states on equal footing. Purpose: In this work, we construct the minimal
complex-energy configuration interaction approach to describe binding energies
and spectra of selected 5 A 11 nuclei. Method: We employ the
complex-energy Gamow shell model (GSM) assuming a rigid He core. The
effective Hamiltonian, consisting of a core-nucleon Woods-Saxon potential and a
simplified version of the Furutani-Horiuchi-Tamagaki interaction with the
mass-dependent scaling, is optimized in the sp space. To diagonalize the
Hamiltonian matrix, we employ the Davidson method and the Density Matrix
Renormalization Group technique. Results: Our optimized GSM Hamiltonian offers
a good reproduction of binding energies and spectra with the root-mean-square
(rms) deviation from experiment of 160 keV. Since the model performs well when
used to predict known excitations that have not been included in the fit, it
can serve as a reliable tool to describe poorly known states. A case in point
is our prediction for the pair of unbound mirror nuclei Li-N in
which a huge Thomas-Ehrman shift dramatically alters the pattern of low-energy
excitations. Conclusion: The new model will enable comprehensive studies of
structure and reactions aspects of light drip-line nuclei.Comment: 11 pages, 3 figure
Strickly finite-range potential for light and heavy nuclei
Strictly finite-range (SFR) potentials are exactly zero beyond their finite range. Single-particle energies and densities, as well as S-matrix pole trajectories, are studied in a few SFR potentials suited for the description of neutrons interacting with light and heavy nuclei. The SFR potentials considered are the standard cutoff Woods-Saxon (CWS) potentials and two potentials approaching zero smoothly: the SV potential introduced by Salamon and Vertse [Phys. Rev. C 77, 037302 (2008)] and the SS potential of Sahu and Sahu [Int. J. Mod. Phys. E 21, 1250067 (2012)]. The parameters of these latter potentials were set so that the potentials may be similar to the CWS shape. The range of the SV and SS potentials scales with the cube root of the mass number of the core like the nuclear radius itself. For light nuclei a single term of the SV potential (with a single parameter) is enough for a good description of the neutron-nucleus interaction. The trajectories are compared with a benchmark for which the starting points (belonging to potential depth zero) can be determined independently. Even the CWS potential is found to conform to this benchmark if the range is identified with the cutoff radius. For the CWS potentials some trajectories show irregular shapes, while for the SV and SS potentials all trajectories behave regularly.Fil: Salamon, P.. MTA Institute for Nuclear Research; HungríaFil: Lovas, R. G.. MTA Institute for Nuclear Research; HungríaFil: Id Betan, Rodolfo Mohamed. Universidad Nacional de Rosario. Facultad de Ciencias Exactas, Ingeniería y Agrimensura; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Rosario. Instituto de Física de Rosario (i); ArgentinaFil: Vertse, T.. MTA Institute for Nuclear Research; Hungría. University of Debrecen. Faculty of Informatics; HungríaFil: Balkay, L.. University of Debrecen. Medical and Health Science Center. Institute of Nuclear Medicine; Hungrí