9,697 research outputs found
Accounting for correlations with core electrons by means of the generalized relativistic effective core potentials: Atoms Hg and Pb and their compounds
A way to account for correlations between the chemically active (valence) and
innermore (core) electrons in the framework of the generalized relativistic
effective core potential (GRECP) method is suggested. The "correlated" GRECP's
(CGRECP's) are generated for the Hg and Pb atoms. Only correlations for the
external twelve and four electrons of them, correspondingly, should be treated
explicitly in the subsequent calculations with these CGRECP's whereas the
innermore electrons are excluded from the calculations. Results of atomic
calculations with the correlated and earlier GRECP versions are compared with
the corresponding all-electron Dirac-Coulomb values. Calculations with the
above GRECP's and CGRECP's are also carried out for the lowest-lying states of
the HgH molecule and its cation and for the ground state of the PbO molecule as
compared to earlier calculations and experimental data. The accuracy for the
vibrational frequencies is increased up to an order of magnitude and the errors
for the bond lengths (rotational constants) are decreased in about two times
when the correlated GRECP's are applied instead of earlier GRECP versions
employing the same innercore-outercore-valence partitioning.Comment: 12 pages, 4 tables, the text of the paper was significantly improve
In-medium modification and decay asymmetry of omega mesons in cold nuclear matter
We discuss an asymmetry of the decay in nuclear matter with
respect to the electron and positron energies. This asymmetry is sensitive to
the properties of the meson self-energy and, in particular, it has a
non-trivial dependence on the energy and momentum. Therefore, this
asymmetry may serve as a powerful tool in studying the properties of the
meson in the nuclear medium.Comment: 19 pages, 9 figure
Electromagnetic modulation of monochromatic neutrino beams
A possibility to produce a modulated monochromatic neutrino beam is
discussed. Monochromatic neutrinos can be obtained in electron capture by
nuclei of atoms or ions, in particular, by nuclei of hydrogen-like ions. It is
shown that monochromatic neutrino beam from such hydrogen-like ions with nuclei
of non-zero spin can be modulated because of different probabilities of
electron capture from hyperfine states. Modulation arises by means of inducing
of electromagnetic transitions between the hyperfine states. Requirements for
the hydrogen-like ions with necessary properties are discussed. A list of the
appropriate nuclei for such ions is presented.Comment: 11 pages, 1 figure, minor corrections to match the final published
versio
Selected vector-meson decay-distributions in reactions of polarized photons with protons
We develop a formalism for studying vector meson () photo-production at
the proton () with polarized photons, , through an
analysis of the decay distribution in the channel . We show
that this decay distribution differs noticeably from the distributions of
purely hadronic decays, like , .
Formulas for the decay distributions are presented which are suitable for data
analysis and interpretation.Comment: 3 pages, 2 figure
Isoscalar-Isovector Interferences in Reactions as a Probe of Baryon Resonance Dynamics
The isoscalar-isovector () interferences in the exclusive
reactions and near the
threshold leads to a distinct difference of the dielectron invariant mass
distributions depending on beam energy. The strength of this effect is
determined by the coupling of resonances to the nucleon vector-meson channels
and other resonance properties. Therefore, a combined analysis of these
reactions can be used as a tool for determining the baryon resonance dynamics
May 12 1997 Cme Event: I. a Simplified Model of the Pre-Eruptive Magnetic Structure
A simple model of the coronal magnetic field prior to the CME eruption on May
12 1997 is developed. First, the magnetic field is constructed by superimposing
a large-scale background field and a localized bipolar field to model the
active region (AR) in the current-free approximation. Second, this potential
configuration is quasi-statically sheared by photospheric vortex motions
applied to two flux concentrations of the AR. Third, the resulting force-free
field is then evolved by canceling the photospheric magnetic flux with the help
of an appropriate tangential electric field applied to the central part of the
AR.
To understand the structure of the modeled configuration, we use the field
line mapping technique by generalizing it to spherical geometry. It is
demonstrated that the initial potential configuration contains a hyperbolic
flux tube (HFT) which is a union of two intersecting quasi-separatrix layers.
This HFT provides a partition of the closed magnetic flux between the AR and
the global solar magnetic field. The vortex motions applied to the AR interlock
the field lines in the coronal volume to form additionally two new HFTs pinched
into thin current layers. Reconnection in these current layers helps to
redistribute the magnetic flux and current within the AR in the
flux-cancellation phase. In this phase, a magnetic flux rope is formed together
with a bald patch separatrix surface wrapping around the rope. Other important
implications of the identified structural features of the modeled configuration
are also discussed.Comment: 25 pages, 11 figures, to appear in ApJ 200
Metallic proximity effect in ballistic graphene with resonant scatterers
We study the effect of resonant scatterers on the local density of states in
a rectangular graphene setup with metallic leads. We find that the density of
states in a vicinity of the Dirac point acquires a strong position dependence
due to both metallic proximity effect and impurity scattering. This effect may
prevent uniform gating of weakly-doped samples. We also demonstrate that even a
single-atom impurity may essentially alter electronic states at low-doping on
distances of the order of the sample size from the impurity.Comment: 9 pages, 2 figure
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