399 research outputs found
One-loop self-energy correction in a strong binding field
A new scheme for the numerical evaluation of the one-loop self-energy
correction to all orders in Z \alpha is presented. The scheme proposed inherits
the attractive features of the standard potential-expansion method but yields a
partial-wave expansion that converges more rapidly than in the other methods
reported in the literature.Comment: 8 pages, 4 table
Multipole expansions in four-dimensional hyperspherical harmonics
The technique of vector differentiation is applied to the problem of the
derivation of multipole expansions in four-dimensional space. Explicit
expressions for the multipole expansion of the function r^n C_j (\hr) with
\vvr=\vvr_1+\vvr_2 are given in terms of tensor products of two
hyperspherical harmonics depending on the unit vectors \hr_1 and \hr_2. The
multipole decomposition of the function (\vvr_1 \cdot \vvr_2)^n is also
derived. The proposed method can be easily generalised to the case of the space
with dimensionality larger than four. Several explicit expressions for the
four-dimensional Clebsch-Gordan coefficients with particular values of
parameters are presented in the closed form.Comment: 19 pages, no figure
QED calculation of the 2p3/2-2p1/2 transition energy in five-electron ion of argon
We perform ab initio QED calculation of the (1s)^2(2s)^22p_{3/2} -
(1s)^2(2s)^22p_{1/2} transition energy in the five-electron ion of argon. The
calculation is carried out by perturbation theory starting with an effective
screening potential approximation. Four different types of the screening
potentials are considered. The rigorous QED calculations of the two
lowest-order QED and electron-correlation effects are combined with approximate
evaluations of the third- and higher-order electron-correlation contributions.
The theoretical value for the wavelength obtained amounts to 441.261(70) (nm,
air) and perfectly agrees with the experimental one, 441.2559(1) (nm, air).Comment: 10 pages, 3 figures, 1 tabl
Optical Lattice Polarization Effects on Hyperpolarizability of Atomic Clock Transitions
The light-induced frequency shift due to the hyperpolarizability (i.e. terms
of second-order in intensity) is studied for a forbidden optical transition,
=0=0. A simple universal dependence on the field ellipticity is
obtained. This result allows minimization of the second-order light shift with
respect to the field polarization for optical lattices operating at a magic
wavelength (at which the first-order shift vanishes). We show the possibility
for the existence of a magic elliptical polarization, for which the
second-order frequency shift vanishes. The optimal polarization of the lattice
field can be either linear, circular or magic elliptical. The obtained results
could improve the accuracy of lattice-based atomic clocks.Comment: 4 pages, RevTeX4, 2 eps fig
Dunajski generalization of the second heavenly equation: dressing method and the hierarchy
Dunajski generalization of the second heavenly equation is studied. A
dressing scheme applicable to Dunajski equation is developed, an example of
constructing solutions in terms of implicit functions is considered. Dunajski
equation hierarchy is described, its Lax-Sato form is presented. Dunajsky
equation hierarchy is characterized by conservation of three-dimensional volume
form, in which a spectral variable is taken into account.Comment: 13 page
Ultrastable Optical Clock with Neutral Atoms in an Engineered Light Shift Trap
An ultrastable optical clock based on neutral atoms trapped in an optical
lattice is proposed. Complete control over the light shift is achieved by
employing the transition of
atoms as a "clock transition". Calculations of ac multipole polarizabilities
and dipole hyperpolarizabilities for the clock transition indicate that the
contribution of the higher-order light shifts can be reduced to less than 1
mHz, allowing for a projected accuracy of better than .Comment: 4 pages, 2 figures, accepted for publication in Phys. Rev. Let
Rescattering effects in laser-assisted electron-atom bremsstrahlung
Rescattering effects in nonresonant spontaneous laser-assisted electron-atom
bremsstrahlung (LABrS) are analyzed within the framework of time-dependent
effective-range (TDER) theory. It is shown that high energy LABrS spectra
exhibit rescattering plateau structures that are similar to those that are
well-known in strong field laser-induced processes as well as those that have
been predicted theoretically in laser-assisted collision processes. In the
limit of a low-frequency laser field, an analytic description of LABrS is
obtained from a rigorous quantum analysis of the exact TDER results for the
LABrS amplitude. This amplitude is represented as a sum of factorized terms
involving three factors, each having a clear physical meaning. The first two
factors are the exact field-free amplitudes for electron-atom bremsstrahlung
and for electron-atom scattering, and the third factor describes free electron
motion in the laser field along a closed trajectory between the first
(scattering) and second (rescattering) collision events. Finally, a
generalization of these TDER results to the case of LABrS in a Coulomb field is
discussed
Relativistic polarization analysis of Rayleigh scattering by atomic hydrogen
A relativistic analysis of the polarization properties of light elastically
scattered by atomic hydrogen is performed, based on the Dirac equation and
second order perturbation theory. The relativistic atomic states used for the
calculations are obtained by making use of the finite basis set method and
expressed in terms of splines and polynomials. We introduce two
experimental scenarios in which the light is circularly and linearly polarized,
respectively. For each of these scenarios, the polarization-dependent angular
distribution and the degrees of circular and linear polarization of the
scattered light are investigated as a function of scattering angle and photon
energy. Analytical expressions are derived for the polarization-dependent
angular distribution which can be used for scattering by both hydrogenic as
well as many-electron systems. Detailed computations are performed for Rayleigh
scattering by atomic hydrogen within the incident photon energy range 0.5 to 10
keV. Particular attention is paid to the effects that arise from higher
(nondipole) terms in the expansion of the electron-photon interaction.Comment: 8 pages, 5 figure
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