14 research outputs found
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
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
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
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
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
Living on the edge of stability, the limits of the nuclear landscape
A first-principles description of nuclear systems along the drip lines
presents a substantial theoretical and computational challenge. In this paper,
we discuss the nuclear theory roadmap, some of the key theoretical approaches,
and present selected results with a focus on long isotopic chains. An important
conclusion, which consistently emerges from these theoretical analyses, is that
three-nucleon forces are crucial for both global nuclear properties and
detailed nuclear structure, and that many-body correlations due to the coupling
to the particle continuum are essential as one approaches particle drip lines.
In the quest for a comprehensive nuclear theory, high performance computing
plays a key role.Comment: Contribution to proceedings of Nobel Symposium 152: Physics with
radioactive beams, June 2012, Gothenburg, Swede
Halos and related structures
The halo structure originated in nuclear physics but is now encountered more
widely. It appears in loosely bound, clustered systems where the spatial
extension of the system is significantly larger than that of the binding
potentials. A review is given on our current understanding of these structures,
with an emphasis on how the structures evolve as more cluster components are
added, and on the experimental situation concerning halo states in light
nuclei.Comment: 27 pages, 3 figures, Contribution to Nobel Symposium 152 "Physics
With Radioactive Beams
Gamow Shell Model Description of Weakly Bound Nuclei and Unbound Nuclear States
We present the study of weakly bound, neutron-rich nuclei using the nuclear
shell model employing the complex Berggren ensemble representing the bound
single-particle states, unbound Gamow states, and the non-resonant continuum.
In the proposed Gamow Shell Model, the Hamiltonian consists of a one-body
finite depth (Woods-Saxon) potential and a residual two-body interaction. We
discuss the basic ingredients of the Gamow Shell Model. The formalism is
illustrated by calculations involving {\it several} valence neutrons outside
the double-magic core: He and O.Comment: 19 pages, 20 encapsulated PostScript figure
and decay of the Be neutron halo ground state
International audienceBeta-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