1,513 research outputs found
Origin of Borromean systems
The complex energies of the three-body resonances for one infinitely heavy
particle and two non-interacting light particles are the sum of the two
contributing two-body complex resonance energies. The bound state of a
Borromean system originates from a resonance when the third interaction is
introduced, a finite mass is allowed and proper angular momentum coupling is
included. The relative importance of these contributions are investigated and
the resulting structure of Borromean systems are traced back to the two-body
continuum properties. The and states in He result from
neutron-core p-states and the ground and first excited state of Li
originate from neutron-core and -states.Comment: Physics Letters B, in pres
Anatomy of three-body decay I. Schematic models
Sequential three-body decay proceeds via spatially confined quasi-stationary
two-body configurations. Direct three-body decay populates the three-body
continuum without intermediate steps. The relative importance of these decay
modes is discussed in a schematic model employing only Coulomb or centrifugal
barrier potentials. Decisive dimensionless charge, mass and energy ratios are
derived. Sequential decay is usually favored for charged particles. Small
charge and small mass of high energy is preferably emitted first. Without
Coulomb potential the sequential decay is favored except when both resonance
energy and intermediate two-body energy are large.Comment: To be published in Nuclear Physics
Momentum distributions of particles from three-body halo fragmentation: Final state interactions
4 págs.; 3 figs.; 1 tab. ; PACS number (s): 25.60.2t, 21.45.1v, 21.60.Gx, 27.20.1nMomentum distributions of particles from nuclear breakup of fast three-body halos are calculated consistently, and applied to Li-11. The same two-body interactions between the three particles are used to calculate the ground state structure and the final state of the reaction processes. We reproduce the available momentum distributions from Li-11 fragmentation, together with the size and energy of Li-11, with a neutron-core relative state containing ap-state admixture of 20%-30%. The available fragmentation data strongly suggest an s state in Li-10 at about 50 keV and indicate a p state around 500 keV. ©1996 American Physical SocietyOne of us (E.G.) acknowledges support from the European
Union through the Human Capital and Mobility program
Contract No. ERBCHBGCT930320Peer Reviewe
Three-body bremsstrahlung and the rotational character of the 12C spectrum
22 págs.; 11 figs.; 6 tabs.; PACS number(s): 23.20.−g, 21.60.Gx, 21.45.−v, 27.20.+nThe electric quadrupole transitions between 0+,2+, and 4+ states in C12 are investigated in a 3α model. The three-body wave functions are obtained by means of the hyperspherical adiabatic expansion method, and the continuum is discretized by imposing a box boundary condition. Corresponding expressions for the continuum three-body (3α) bremsstrahlung and photon dissociation cross sections are derived and computed for two different α−α potentials. The available experimental energy dependence is reproduced and a series of other cross sections are predicted. The transition strengths are defined and derived from the cross sections, and compared to schematic rotational model predictions. The computed properties of the C12 resonances suggest that the two lowest bands are made, respectively, by the states {0+1,2+1,4+2} and {0+2,2+2,4+1}. The transitions between the states in the first band are consistent with the rotational pattern corresponding to three alphas in an equilateral triangular structure. For the second band, the transitions are also consistent with a rotational pattern, but with the three alphas in an aligned arrangement. ©2015 American Physical SocietyThis work was partly supported by funds provided by DGI
of MINECO (Spain) under Contract No. FIS2011-23565.Peer Reviewe
Comment on "New modes of halo excitations in the 6He nucleus"
We try to explain the differences in the 6He dipole strength function in
refs. [1] and [2]. We perform the full basis calculation of the strength
function with the same renormalized interaction as in [1] and show that the
size of the basis, needed for converged calculations of the 6He continuum
spectrum, is much larger than that for the discrete spectrum. The renormalized
interaction of [1] therefore cannot be used for the continuum spectrum
calculations with the same basis as for the ground state.Comment: 2 pages, 3 figure
Resonances in three-body systems with short and long-range interactions
The complex scaling method permits calculations of few-body resonances with
the correct asymptotic behaviour using a simple box boundary condition at a
sufficiently large distance. This is also valid for systems involving more than
one charged particle. We first apply the method on two-body systems. Three-body
systems are then investigated by use of the (complex scaled) hyperspheric
adiabatic expansion method. The case of the 2 resonance in Be and
Li is considered. Radial wave functions are obtained showing the correct
asymptotic behaviour at intermediate values of the hyperradii, where wave
functions can be computed fully numerically.Comment: invited talk at the 18th International Conference on Few-Body
Problems in Physics, Santos-S.Paulo, August 21-26, 200
Three-body structure of the low-lying Ne-states
The Borromean nucleus Ne (O) is investigated by using
the hyperspheric adiabatic expansion for a a three-body system. The measured
size of O and the low-lying resonances of F (O) are
first used as constraints to determine both central and spin-dependent two-body
interactions. Then, the ground state structure of Ne is found to be an
almost equal mixture of and proton-O relative states, the
two lowest excited states have about 80% of -mixed components, and for the
next two excited three-body states the proton-O relative s-states do not
contribute. The spatial extension is as in ordinary nuclei. The widths of the
resonances are estimated by the WKB transmission through the adiabatic
potentials and found in agreement with the established experimental limits. We
compare with experimental information and previous works.Comment: 29 pages, 7 postscript figures, to be published in Nuclear Physics
Isospin mixing and energy distributions in three-body decay
The structure of the second 2 resonance in Li is investigated with
special emphasis on its isospin 0 components. The wave functions are computed
in a three-body model (++) using the hyperspherical adiabatic
expansion method combined with complex scaling. In the decay into three free
particles the symmetry conserving short-range interaction dominates at short
distance whereas the symmetry breaking Coulomb interaction dominates at
intermediate and large distances resulting in substantial isospin mixing. We
predict the mixing and the energy distributions of the fragments after decay.
Computations are consistent with available experiments. We conjecture that
nuclear three-body decays frequently produce such large isospin mixing at large
distance where the energy distributions. are determined.Comment: 5 pages, 4 figures, to be published in Physics Letters
Cluster sum rules for three-body systems with angular-momentum dependent interactions
10 págs.; 3 figs.; 2 tabs.; 1 apéndice ; PACS number(s): 21.45.−v, 11.55.Hx, 23.20.−g, 31.15.xjWe derive general expressions for non-energy-weighted and energy-weighted cluster sum rules for systems of three charged particles. The interferences between pairs of particles are found to play a substantial role. The energy-weighted sum rule is usually determined by the kinetic energy operator, but we demonstrate that it has similar additional contributions from the angular momentum and parity dependence of two- and three-body potentials frequently used in three-body calculations. The importance of the different contributions is illustrated with the dipole excitations in He6. The results are compared with the available experimental data. © 2008 The American Physical Society.This work was partly supported by funds provided by DGI
of MEC (Spain) under contract no. FIS2005-00640. One of us
(R.D.) acknowledges support by a predoctoral I3P fellowship
from CSIC and the European Social Fund.Peer Reviewe
Three-Body Halos. II. from Two- to Three-Body Asymptotics
The large distance behavior of weakly bound three-body systems is
investigated. The Schr\"{o}dinger equation and the Faddeev equations are
reformulated by an expansion in eigenfunctions of the angular part of a
corresponding operator. The resulting coupled set of effective radial equations
are then derived. Both two- and three-body asymptotic behavior are possible and
their relative importance is studied for systems where subsystems may be bound.
The system of two nucleons outside a core is studied numerically in detail and
the character of possible halo structure is pointed out and investigated.Comment: 16 pages, compressed and uuencoded PosrScript file, IFA-94/3
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