32,552 research outputs found
On the photoionization of the outer electrons in noble gas endohedral atoms
We demonstrate the prominent modification of the outer shell photoionization
cross-section in noble gas (NG) endohedral atoms NG@F under the action of the
fullerene F electron shell. This shell leads to two important effects, namely
to strong enhancement of the cross-section due to fullerenes shell polarization
under the action of the incoming electromagnetic wave and to prominent
oscillation of this cross-section due to the reflection of the photoelectron
from NG by the F shell.
All but He noble gas atoms are considered. The polarization of the fullerene
shell is expressed via the total photoabsorption cross-section of F. The
reflection of the photoelectron is taken into account in the frame of the
so-called bubble potential that is a spherical zero --thickness potential.
It is assumed in the derivations that NG is centrally located in the
fullerene. It is assumed also, in accord with the existing experimental data,
that the fullerenes radius R is much bigger than the atomic radius and the
thickness of the fullerenes shell . These assumptions permit, as it was
demonstrated recently, to present the NG@F photoionization cross-section as a
product of the NG cross-section and two well defined calculated factors.Comment: 19 pages, 9 figure
Large-scale magnetic fields, curvature fluctuations and the thermal history of the Universe
It is shown that gravitating magnetic fields affect the evolution of
curvature perturbations in a way that is reminiscent of a pristine
non-adiabatic pressure fluctuation. The gauge-invariant evolution of curvature
perturbations is used to constrain the magnetic power spectrum. Depending on
the essential features of the thermodynamic history of the Universe, the
explicit derivation of the bound is modified. The theoretical uncertainty in
the constraints on the magnetic energy spectrum is assessed by comparing the
results obtained in the case of the conventional thermal history with the
estimates stemming from less conventional (but phenomenologically allowed)
post-inflationary evolutions.Comment: 21 pages, 6 included figure
Pentaquark implications for exotic mesons
If the exotic baryon is a correlated with , then there should exist an exotic meson, GeV with width MeV. The
may be broad members of {\bf 10} \10bar in such a
picture. Vector mesons in the 1.4 - 1.7GeV mass range are also compared with
this picture
Non-dipole angular anisotropy parameters of semi-filled shell atoms
We present the results of calculations of outer shell non-dipole angular
anisotropy parameters for semi-filled shell atoms in the Hartree-Fock (HF)
one-electron approximation and with account of inter-electron correlations in
the frame of the Spin Polarized Random Phase Approximation with Exchange (SP
RPAE). We demonstrate for the first time that this characteristic of
photoionization process is essentially sensitive to the fact whether the
photoelectron has the same or opposite spin orientation to that of the
semi-filled shell.Comment: 15 pages, 8 figure
Lepton Flavor Violation without Supersymmetry
We study the lepton flavor violating (LFV) processes mu -> e gamma, mu -> 3e,
and mu -> e conversion in nuclei in the left-right symmetric model without
supersymmetry and perform the first complete computation of the LFV branching
ratios B(mu -> f) to leading non-trivial order in the ratio of left- and
right-handed symmetry breaking scales. To this order, B(mu -> e gamma) and B(mu
-> e) are governed by the same combination of LFV violating couplings, and
their ratio is naturally of order unity. We also find B(mu -> 3 e)/B(mu -> e)
\sim 100 under slightly stronger assumptions. Existing limits on the branching
ratios already substantially constrain mass splittings and/or mixings in the
heavy neutrino sector. When combined with future collider studies and precision
electroweak measurements, improved limits on LFV processes will test the
viability of low-scale, non-supersymmetric LFV scenarios.Comment: 24 pages, 7 figures, 2 table
Photoionization of Xe 3d electrons in molecule Xe@C60: interplay of intra-doublet and confinement resonances
We demonstrate rather interesting manifestations of co-existence of resonance
features in characteristics of the photoionization of 3d-electrons in Xe@C60.
It is shown that the reflection of photoelectrons produced by the 3d Xe
photoionization affects greatly partial photoionization cross-sections of and
levels and respective angular anisotropy parameters, both dipole and non-dipole
adding to all of them additional maximums and minimums. The calculations are
performed treating the 3/2 and 5/2 electrons as electrons of different kinds
with their spins "up" and "down". The effect of C60 shell is accounted for in
the frame of the "orange" skin potential model.Comment: 13 pages, 12 figure
An Elementary Proof of the Existence and Uniqueness Theorem for the Navier-Stokes Equations
We give a geometric approach to proving know regularity and existence
theorems for the 2D Navier-Stokes Equations. We feel this point of view is
instructive in better understanding the dynamics. The technique is inspired by
constructions in the Dynamical Systems.Comment: 15 Page
Two-electron photoionization of endohedral atoms
Using as an example, we demonstrate that static potential of the
fullerene core essentially alters the cross section of the two-electron
ionization differential in one-electron energy . We found that at high photon energy prominent oscillations
appear in it due to reflection of the second, slow electron wave on the shell, which "dies out" at relatively high values, of about
23 two-electron ionization potentials. The results were presented for
ratios , where is the two-electron differential
photoionization cross section. We have calculated the ratio , that accounts for
reflection of both photoelectrons by the shell. We have calculated
also the value of two-electron photoionization cross section and found that this value is close to that of an isolated
atom.Comment: 13 pages, 4 figure
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