342 research outputs found
Relativistic wave and Green's functions for hydrogen--like ions
The \textsc{Greens} library is presented which provides a set of C++
procedures for the computation of the (radial) Coulomb wave and Green's
functions. Both, the nonrelativistic as well as relativistic representations of
these functions are supported by the library. However, while the wave functions
are implemented for all, the bound and free--electron states, the Green's
functions are provided only for bound--state energies ). Apart from the
Coulomb functions, moreover, the implementation of several special functions,
such as the Kummer and Whittaker functions of the first and second kind, as
well as a few utility procedures may help the user with the set--up and
evaluation of matrix elements.Comment: 21 page
High-fidelity copies from a symmetric 1 to 2 quantum cloning machine
A symmetric 1 to 2 quantum cloning machine (QCM) is presented that provides
high-fidelity copies with for all pure (single-qubit)
input states from a given meridian of the Bloch sphere. \cor{Emphasize is
placed especially on the states of the (so-called) Eastern meridian, that
includes the computational basis states \ketm{0}, \ketm{1} together with the
diagonal state \ketm{+} = \frac{1}{\sqrt{2}} (\ketm{0}
+ \ketm{1}), for which suggested cloning transformation is shown to be
optimal.} In addition, we also show how this QCM can be utilized for
eavesdropping in Bennett's B92 protocol for quantum key distribution with a
substantial higher success rate than obtained for universal or equatorial
quantum copying.Comment: 2 figures, 20 reference
Photon Emission from Hollow Ions Near Surfaces
Ions with multiple inner-shell vacancies frequently arise due to their interaction with different targets, such as (intense) light pulses, atoms, clusters or bulk material. They are formed, in addition, if highly charged ions approach surfaces and capture electrons at rather large distances. To explore the interaction of such hollow ions and their subsequent relaxation, photon spectra in different frequency regions have been measured and compared to calculations. To support these and related measurements, we here show within the framework of the Jena Atomic Calculator ( Jac ) how (additional) electrons in outer shells modify photon emission and lead to characteristic shifts in the observed spectra. Further, for highly charged Ar ions in KL m ( m = 1 … 8 ) configurations, we analyze the mean relaxation time for their stabilization into the different ground configurations. These examples demonstrate how a powerful and flexible toolbox such as Jac will be useful (and necessary) in order to model the photon and electron emission of ions as they occur not only near surfaces but also in astro-, atomic and plasma physics
Relativistic central--field Green's functions for the RATIP package
From perturbation theory, Green's functions are known for providing a simple
and convenient access to the (complete) spectrum of atoms and ions. Having
these functions available, they may help carry out perturbation expansions to
any order beyond the first one. For most realistic potentials, however, the
Green's functions need to be calculated numerically since an analytic form is
known only for free electrons or for their motion in a pure Coulomb field.
Therefore, in order to facilitate the use of Green's functions also for atoms
and ions other than the hydrogen--like ions, here we provide an extension to
the Ratip program which supports the computation of relativistic
(one--electron) Green's functions in an -- arbitrarily given -- central--field
potential \rV(r). Different computational modes have been implemented to
define these effective potentials and to generate the radial Green's functions
for all bound--state energies . In addition, care has been taken to
provide a user--friendly component of the Ratip package by utilizing features
of the Fortran 90/95 standard such as data structures, allocatable arrays, or a
module--oriented design.Comment: 20 pages, 1 figur
Program to calculate pure angular momentum coefficients in jj-coupling
A program for computing pure angular momentum coefficients in relativistic
atomic structure for any scalar one- and two-particle operator is presented.
The program, written in Fortran 90/95 and based on techniques of second
quantization, irreducible tensorial operators, quasispin and the theory of
angular momentum, is intended to replace existing angular coefficient modules
from GRASP92. The new module uses a different decomposition of the coefficients
as sums of products of pure angular momentum coefficients, which depend only on
the tensor rank of the interaction but not on its details, with effective
interaction strengths of specific interactions. This saves memory and reduces
the computational cost of big calculations signficantly
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
Hyperfine-induced effects on the linear polarization of the K emission from helium-like ions
The linear polarization of the characteristic photon emission from
few-electron ions is studied for its sensitivity with regard to the nuclear
spin and magnetic moment of the ions. Special attention is paid, in particular,
to the K (1s 2p_{3/2} ^{1,3}P_{1,2} \to 1s^2 ^1S_0) decay of
selected helium-like ions following the radiative electron capture into
initially hydrogen-like species. Based on the density matrix theory, a unified
description is developed that includes both, the many-electron and hyperfine
interactions as well as the multipole-mixing effects arising from the expansion
of the radiation field. It is shown that the polarization of the K
line can be significantly affected by the mutipole mixing between the leading
and hyperfine-induced components of 1s2p ^3P_2, F_i \to 1s^2 ^1S_0,
F_f transitions. This - mixing strongly depends on the nuclear
properties of the considered isotopes and can be addressed experimentally at
existing heavy-ion storage rings
Strong-Field Ionization Amplitudes for Atomic Many-Electron Targets
The strong-field approximation (SFA) has been widely applied in the literature to model the ionization of atoms and molecules by intense laser pulses. A recent re-formulation of the SFA in terms of partial waves and spherical tensor operators helped adopt this approach to account for realistic atomic potentials and pulses of different shape and time structure. This re-formulation also enables one to overcome certain limitations of the original SFA formulation with regard to the representation of the initial-bound and final-continuum wave functions of the emitted electrons. We here show within the framework of Jac , the Jena Atomic Calculator, how the direct SFA ionization amplitude can be readily generated and utilized in order to compute above-threshold ionization (ATI) distributions for many-electron targets and laser pulses of given frequency, intensity, polarization, pulse duration and carrier–envelope phase. Examples are shown for selected ATI energy, angular as well as momentum distributions in the strong-field ionization of atomic krypton. We also briefly discuss how this approach can be extended to incorporate rescattering and high-harmonic processes into the SFA amplitudes
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