1,648 research outputs found
Anomalous population of He states in reactions with Li
Structure with the lowest energy observed in the He spectrum populated
in the proton knockout reaction with Li beam has a peak at
MeV. This peak is usually interpreted as a resonant ground state of
He. Our theoretical calculations indicate that this peak is likely to be
a pileup of , , and excitations with very similar shapes. %We
predict a very specific nature of the excitation in He. Moreover,
the ``soft'' excitation appears to be the lowest one in energy. Such an
anomalous continuum response is traced to the halo structure of Li
providing extreme low energy shift to all the expected continuum excitations.
Competitions of the initial state structure (ISS) and the final state
interaction (FSI) effects on the spectrum and three-body correlations in
He are discussed. Analogous effect of the extreme low-energy shift could
also be expected in other cases of emitters populated in reactions with
halo nuclei. Simplified example of the He spectrum in knockout
from Be, is given. We also discuss limits on the properties of He
stemming from the observed He spectrum.Comment: 10 pages, 13 figure
Thomas-Ehrman effect in a three-body model: Ne case
The dynamic mechanism of the Thomas-Ehrman shift is studied in three-cluster
systems by example of Ne and C isobaric mirror partners. We
predict configuration mixings for and states in Ne and
C. Large isospin symmetry breaking on the level of wave function
component weights is demonstrated for these states and discussed as three-body
mechanism of Thomas-Ehrman shift. It is shown that the description of the
Coulomb displacement energies requires a consistency among three parameters:
the Ne decay energy , the F ground state energy , and
the configuration mixing parameters for the Ne/C and
states. Basing on this analysis we infer the F ground state
energy to be MeV.Comment: 10 pages 8 figure
Optimal control of electromagnetic field using metallic nanoclusters
The dielectric properties of metallic nanoclusters in the presence of an
applied electromagnetic field are investigated using non-local linear response
theory. In the quantum limit we find a non-trivial dependence of the induced
field and charge distribution on the spatial separation between the clusters
and on the frequency of the driving field. Using a genetic algorithm, these
quantum functionalities are exploited to custom-design sub-wavelength lenses
with a frequency controlled switching capability.Comment: accepted for publication in New Journal of Physic
Negative phase velocity in nonlinear oscillatory systems --mechanism and parameter distributions
Waves propagating inwardly to the wave source are called antiwaves which have
negative phase velocity. In this paper the phenomenon of negative phase
velocity in oscillatory systems is studied on the basis of periodically paced
complex Ginzbug-Laundau equation (CGLE). We figure out a clear physical picture
on the negative phase velocity of these pacing induced waves. This picture
tells us that the competition between the frequency of the
pacing induced waves with the natural frequency of the oscillatory
medium is the key point responsible for the emergence of negative phase
velocity and the corresponding antiwaves. and
are the criterions for the waves with negative
phase velocity. This criterion is general for one and high dimensional CGLE and
for general oscillatory models. Our understanding of antiwaves predicts that no
antispirals and waves with negative phase velocity can be observed in excitable
media
Pauli-principle driven correlations in four-neutron nuclear decays
Mechanism of simultaneous non-sequential four-neutron () emission (or
`true' -decay) has been considered in phenomenological five-body approach.
This approach is analogous to the model of the direct decay to the continuum
often applied to - and -decays. It is demonstrated that -decay
fragments should have specific energy and angular correlations reflecting
strong spatial correlations of `valence' nucleons orbiting in their
-precursors. Due to the Pauli exclusion principle, the valence neutrons are
pushed to the symmetry-allowed configurations in the -precursor structure,
which causes a `Pauli focusing' effect. Prospects of the observation of the
Pauli focusing have been considered for the -precursors H and O.
Fingerprints of their nuclear structure or/and decay dynamics are predicted
Negative Refractive Index in Artificial Metamaterials
We discuss optical constants in artificial metamaterials showing negative
magnetic permeability and electric permittivity. Using effective field theory,
we calculate effective permeability of nanofabricated media composed of pairs
of identical gold nano-pillars with magnetic response in the visible spectrum.Comment: 16 pages, 4 figures, submitted to Optics Letter
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