197 research outputs found
Atomic swelling upon compression
The hydrogen atom under the pressure of a spherical penetrable confinement
potential of a decreasing radius is explored, as a case study. A novel
counter-intuitive effect of atomic swelling rather than shrinking with
decreasing is unraveled, when reaches, and remains smaller
than, a certain critical value. Upon swelling, the size of the atom is shown to
increase by an order of magnitude, or more, compared to the size of the free
atom. Examples of changes of photoabsorption properties of confined hydrogen
atom upon its swelling are uncovered and demonstrated.Comment: 5 pages, 4 figure
Ground state properties of a confined simple atom by C fullerene
We numerically study the ground state properties of endohedrally confined
hydrogen (H) or helium (He) atom by a molecule of C. Our study is based
on Diffusion Monte Carlo method. We calculate the effects of centered and small
off-centered H- or He-atom on the ground state properties of the systems and
describe the variation of ground state energies due to the C parameters
and the confined atomic nuclei positions. Finally, we calculate the electron
distributions in plane in a wide range of C parameters.Comment: 23 pages, 9 figures. To appear in J.Phys. B: Atom. Mol. Op
Term-dependent hybridization of the 5 f-wave functions of Ba and Ba++
It is shown that, unlike in neutral Ba, the 4d→5f transitions cannot be neglected in the interpretation of the 4d spectrum of Ba++. A term-dependent hybridization of the 5f wave functions occurs, the effects of which reverse between Ba and Ba++, and oscillator strength reappears in the 4d→nf (n>~5) transitions. A second kind of wave-function collapse is identified and its effects are described
The Mobility of Researchers as the Vector of Innovation in Europe and Beyond
Рассматривается политика поддержки инноваций в Европейском Союзе, в частности перемещение ученых и создание единого исследовательского пространства
Magneto-optical rotation of spectrally impure fields and its nonlinear dependence on optical density
We calculate magneto-optical rptation of spectrally impure fileds in an
optically thick cold atmic medium. We show that the spectral impurity leads to
non-linear dependence of the rotation angle on optical density. Using our
calculations, we provide a quanttative analysis of the recent experimental
results of G. Labeyrie et al. [Phys. Rev. A 64, 033402 (2001)] using cold
Rb atoms.Comment: 6 pages, 5 Figures, ReVTeX4, Submitted to PR
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
Statistics of electromagnetic transitions as a signature of chaos in many-electron atoms
Using a configuration interaction approach we study statistics of the dipole
matrix elements (E1 amplitudes) between the 14 lower odd states with J=4 and
21st to 100th even states with J=4 in the Ce atom (1120 lines). We show that
the distribution of the matrix elements is close to Gaussian, although the
width of the Gaussian distribution, i.e. the root-mean-square matrix element,
changes with the excitation energy. The corresponding line strengths are
distributed according to the Porter-Thomas law which describes statistics of
transition strengths between chaotic states in compound nuclei. We also show
how to use a statistical theory to calculate mean squared values of the matrix
elements or transition amplitudes between chaotic many-body states. We draw
some support for our conclusions from the analysis of the 228 experimental line
strengths in Ce [J. Opt. Soc. Am. v. 8, p. 1545 (1991)], although direct
comparison with the calculations is impeded by incompleteness of the
experimental data. Nevertheless, the statistics observed evidence that highly
excited many-electron states in atoms are indeed chaotic.Comment: 16 pages, REVTEX, 4 PostScript figures (submitted to Phys Rev A
Giant resonances of endohedral atoms
We demonstrate for the first time that the effect of fullerene shell upon
photoionization of the "caged" atom in an endohedral can result in formation of
Giant Endohedral Resonances or GER. This is illustrated by the concrete case of
Xe@C60 photoionization cross-section that exhibits at 17 eV a powerful
resonance with total oscillator strengths of about 25. The prominent
modification of the 5p6 electron photoionization cross-section of Xe@C60 takes
place due to strong fullerene shell polarization under the action of the
incoming electromagnetic wave and oscillation of this cross-section due to the
reflection of the photoelectron from Xe by the C60. These two factors transform
the smoothly decreasing 5p6 cross-section of Xe into a rather complex curve
with a powerful maximum for Xe@C60, with the oscillator strength being equal to
25! We present also the results for the dipole angular anisotropy parameter
that is strongly affected by the reflection of the photoelectron waves but not
modified by C60 polarization. The polarization of C60 is expressed via its
total photoabsorption cross-section. The reflection of the photoelectron is
taken into account in the frame of the so-called bubble potential that is a
spherical delta-type potential.Comment: 7pages, 3 figures, 14 references,some previous references are remove
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