429 research outputs found
Relativistic configuration-interaction calculation of energy levels of core-excited states in lithium-like ions: argon through krypton
Large-scale relativistic configuration-interaction calculation of energy
levels of core-excited states of lithium-like ions is presented. Quantum
electrodynamic, nuclear recoil, and frequency-dependent Breit corrections are
included in the calculation. The approach is consistently applied for
calculating all core-excited states for all lithium-like ions starting
from argon () and ending with krypton (). The results obtained
are supplemented with systematical estimations of calculation errors and
omitted effects
Relativistic calculation of the two-photon decay rate of highly-excited ionic states
Based on quantum electrodynamics, we reexamine the two-photon decay of
one-electron atoms. Special attention is paid to the calculation of the
(two-photon) total decay rates which can be viewed as the imaginary part of the
two-loop self-energy. We argue that our approach can easily be applied to the
cases with a virtual state having an intermediate energy between the initial
and the final state of the decay process leading, thus, to the resonance peaks
in the two-photon energy distribution. In order to illustrate our approach, we
obtain fully relativistic results, resolved into electric and magnetic
multipole components, for the two-photon decay rates of the 3S_{1/2} ->
1S_{1/2} transition in neutral hydrogen as well as in various hydrogen-like
ions.Comment: 11 pages, LaTe
Compton scattering of twisted light: angular distribution and polarization of scattered photons
Compton scattering of twisted photons is investigated within a
non-relativistic framework using first-order perturbation theory. We formulate
the problem in the density matrix theory, which enables one to gain new
insights into scattering processes of twisted particles by exploiting the
symmetries of the system. In particular, we analyze how the angular
distribution and polarization of the scattered photons are affected by the
parameters of the initial beam such as the opening angle and the projection of
orbital angular momentum. We present analytical and numerical results for the
angular distribution and the polarization of Compton scattered photons for
initially twisted light and compare them with the standard case of plane-wave
light
Caustic structures in the spectrum of x-ray Compton scattering off electrons driven by a short intense laser pulse
We study the Compton scattering of x-rays off electrons that are driven by a
relativistically intense short optical laser pulse. The frequency spectrum of
the laser-assisted Compton radiation shows a broad plateau in the vicinity of
the laser-free Compton line due to a nonlinear mixing between x-ray and laser
photons. Special emphasis is placed on how the shape of the short assisting
laser pulse affects the spectrum of the scattered x-rays. In particular, we
observe sharp peak structures in the plateau region, whose number and locations
are highly sensitive to the laser pulse shape. These structures are interpreted
as spectral caustics by using a semiclassical analysis of the laser-assisted
QED matrix element
Double lepton pair production with electron capture in relativistic heavy--ion collisions
We present a theoretical study of a double lepton pair production in
ultra--relativistic collision between two bare ions. Special emphasis is placed
to processes in which creation of (at least one) pair is accompanied
by the capture of an electron into a bound ionic state. To evaluate the
probability and cross section of these processes we employ two approaches based
on (i) the first--order perturbation theory and multipole expansion of Dirac
wavefunctions, and (ii) the equivalent photon approximation. With the help of
such approaches, detailed calculations are made for the creation of two
bound--free pairs as well as of bound--free and free--free
pairs in collisions of bare lead ions Pb. The results of
the calculations indicate that observation of the double lepton processes may
become feasible at the LHC facility.Comment: 12 pages, 1 figur
The effect of bound state dressing in laser assisted radiative recombination
We present a theoretical study on the recombination of a free electron into
the ground state of a hydrogen-like ion in the presence of an external laser
field. Emphasis is placed on the effects caused by the laser dressing of the
residual ionic bound state. To investigate how this dressing affects the total
and angle-differential cross section of laser assisted radiative recombination
(LARR) we apply first-order perturbation theory and the separable
Coulomb-Volkov-continuum ansatz. Using this approach detailed calculations were
performed for low- hydrogen like ions and laser intensities in the range
from to . It is seen that
the total cross section as a function of the laser intensity is remarkably
affected by the bound state dressing. Moreover the laser dressing becomes
manifest as asymmetries in the angular distribution and the (energy) spectrum
of the emitted recombination photons.Comment: 9 pages, 5 figure
Bessel beams of two-level atoms driven by a linearly polarized laser field
We study Bessel beams of two-level atoms that are driven by a linearly
polarized laser field. Starting from the Schroedinger equation, we determine
the states of two-level atoms in a plane-wave field respecting propagation
directions both of the atom and the field. For such laser-driven two-level
atoms, we construct Bessel beams beyond the typical paraxial approximation. We
show that the probability density of these atomic beams obtains a non-trivial,
Bessel-squared-type behavior and can be tuned under the special choice of the
atom and laser parameters, such as the nuclear charge, atom velocity, laser
frequency, and propagation geometry of the atom and laser beams. Moreover, we
spatially and temporally characterize the beam of hydrogen and selected
(neutral) alkali-metal atoms that carry non-zero orbital angular momentum
(OAM). The proposed spatiotemporal Bessel states (i) are able to describe, in
principle, twisted states of any two-level system which is driven by the
radiation field and (ii) have potential applications in atomic, nuclear
processes and quantum communication.Comment: 13 pages, 5 figures, appeared as a EPJD highlight on Thursday, 01
August 2013
http://www.epj.org/index.php?option=com_content&view=article&id=684%3Aepjd-highlight-novel-beams-made-of-twisted-atoms&catid=112%3Aepj-d&Itemid=466&lang=e
- …