55 research outputs found
Exceptional points in the scattering continuum
The manifestation of exceptional points in the scattering continuum of atomic
nucleus is studied using the real-energy continuum shell model. It is shown
that low-energy exceptional points appear for realistic values of coupling to
the continuum and, hence, could be accessible experimentally. Experimental
signatures are proposed which include the jump by of the elastic
scattering phase shift and a salient energy dependence of cross-sections in the
vicinity of the exceptional point.Comment: 7 pages, 9 figure
Near-threshold correlations of neutrons
The appearance of charged-particle clustering in near-threshold configuration
is a phenomenon that can be explained in the Open Quantum System description of
the atomic nucleus. In this work we apply the realistic Shell Model Embedded in
the Continuum to elucidate the emergence of neutron correlations in
near-threshold many-body states coupled to l=1,2 neutron decay channels.
Spectral consequences of such continuum coupling are briefly discussed together
with the emergence of complex multi-neutron correlations.Comment: Invited talk at XXXIII Mazurian Lakes Conference on Physic
Chaos induced by Pauli blocking
Dynamics of classical scattering in the system of fermions is studied. The
model is based on the coherent state representation and the equations of motion
for fermions are derived from the time-dependent variational principle. It is
found that the antisymmetrization due to the Pauli exclusion principle, may
lead to hyperbolic chaotic scattering even in the absence of interaction
between particles. At low bombarding energies, the same effect leads to the
screening of the hard, short-ranged component in the two particle interaction
and thus regularizes the dynamics.Comment: 10 pages, LaTeX
Asymptotic normalization coefficients and continuum coupling in mirror nuclei
Background: An asymptotic normalization coefficient (ANC) characterizes the
asymptotic form of a one-nucleon overlap integral required for description of
nucleon-removal reactions. Purpose: We investigate the impact of the particle
continuum on proton and neutron ANCs for mirror systems from - and
-shell regions. Method: We use the real-energy and complex-energy continuum
shell model approaches. Results: We studied the general structure of the
single-particle ANCs as a function of the binding energy and orbital angular
momentum. We computed ANCs in mirror nuclei for different physical situations,
including capture reactions to weakly-bound and unbound states. Conclusions: We
demonstrated that the single-particle ANCs exhibit generic behavior that is
different for charged and neutral particles. We verified the previously
proposed relation [N.K. Timofeyuk, R.C. Johnson, and A.M. Mukhamedzhanov, Phys.
Rev. Lett. 91, 232501 (2003); Phys. Rev. Lett. 97, 069904(E) (2006); N. K.
Timofeyuk and P. Descouvemont, Phys. Rev. C 72, 064324 (2005)] between proton
and neutron mirror ANCs. We find minor modifications if the spectroscopic
strength is either localized in a single state or broadly distributed. For
cases when several states couple strongly to the decay channel, these
modifications may reach 30%.Comment: 18 pages, 17 figures, 9 table
and decay of the Be neutron halo ground state
Beta-delayed proton emission from the neutron halo ground state of Be
raised much attention due to the unusually high decay rate. It was argued that
this may be due to the existence of a resonance just above the proton decay
threshold. In this Letter, we use the lenses of real-energy continuum shell
model to describe several observables including the Gamow-Teller rates for the
-delayed and proton decays, and argue that, within our model,
the large branching ratio cannot be reconciled with other
data.Comment: 5 pages, 3 figure
Near-threshold resonances in 11C and the 10B(p,{\alpha})7Be aneutronic reaction cross section
The nucleus 11C plays an important role in the boron-proton fusion reactor
environment as a catalyzer of the 10B(p,{\alpha})7Be reaction which, by
producing a long-lived isotope of 7Be, poisons the aneutronic fusion process
11B(p,2{\alpha})4He. The low-energy cross section of 10B(p,{\alpha})7Be depends
on the near-threshold states 7/2+1 , 5/2+2 , 5/2+3 in 11C whose properties are
primarily known from the indirect measurements. We investigate the
continuum-coupling induced collectivization of these resonances in the shell
model embedded in the continuum. We predict a significant enhancement of the
10B(p,{\alpha})7Be cross section at energies accessible to the laser-driven hot
plasma facilities.Comment: 4 pages, 2 figure
Molecular dynamics approach: from chaotic to statistical properties of compound nuclei
Statistical aspects of the dynamics of chaotic scattering in the classical
model of -cluster nuclei are studied. It is found that the dynamics
governed by hyperbolic instabilities which results in an exponential decay of
the survival probability evolves to a limiting energy distribution whose
density develops the Boltzmann form. The angular distribution of the
corresponding decay products shows symmetry with respect to angle. Time
estimated for the compound nucleus formation ranges within the order of
s.Comment: 11 pages, LaTeX, non
Gamow Shell-Model Description of Weakly Bound and Unbound Nuclear States
Recently, the shell model in the complex k-plane (the so-called Gamow Shell
Model) has been formulated using a complex Berggren ensemble representing bound
single-particle states, single-particle resonances, and non-resonant continuum
states. In this framework, we shall discuss binding energies and energy spectra
of neutron-rich helium and lithium isotopes. The single-particle basis used is
that of the Hartree-Fock potential generated self-consistently by the
finite-range residual interaction.Comment: 13 pages, 2 figures, presented by N. Michel at the XXVII Symposium On
Nuclear Physics, Taxco, Guerrero, Mexico, January 5-8 200
Shell Structure of Exotic Nuclei
Theoretical predictions and experimental discoveries for neutron-rich,
short-lived nuclei far from stability indicate that the familiar concept of
nucleonic shell structure should be considered as less robust than previously
thought. The notion of single-particle motion in exotic nuclei is reviewed with
a particular focus on three aspects: (i) variations of nuclear mean field with
neutron excess due to tensor interactions; (ii) importance of many-body
correlations; and (iii) influence of open channels on properties of weakly
bound and unbound nuclear states.Comment: 14 pages, 7 figures, submitted to Progress in Particle and Nuclear
Physics, Proc. of the International School of Nuclear Physics 28th Course,
Radioactive Beams, Nuclear Dynamics and Astrophysics, Erice-Sicily: 16 - 24
September 200
Theory of the two-proton radioactivity in the continuum shell model
We develop the microscopic description of the two-nucleon radioactivity in
the framework of the Shell Model Embedded in the Continuum. This approach is
applied for the description of spontaneous two-proton radioactivity in
Fe, Ni and Zn.Comment: 61 pages, 5 figure
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