322 research outputs found
Generation of attosecond xuv pulses in strong laser-atom interactions
The generation of radiation pulses that can be as short as 120 attoseconds is demonstrated theoretically. We have employed a two-dimensional exact solution of the Schrodinger equation that allows for arbitrary laser ellipticity. By manipulating the laser ellipticity in time, it is shown that one can control the wave-packet dynamics of the ejected atomic electron. The nonlinear interaction of the electron with the atomic core can thus be restricted to extremely short times. Photon energies up to 160 eV are generated. It is also shown that with a higher laser frequency, even shorter pulses can be produced. [S1050-2947(98)02211-2]
Anatomical variants of the emissary veins: unilateral aplasia of both the sigmoid sinus and the internal jugular vein and development of the petrosquamosal sinus. A rare case report
We report a case of hypoplasia of the right transverse sinus and aplasia of the
ipsilateral sigmoid sinus and the internal jugular vein. In addition, development
of the petrosquamosal sinus and the presence of a large middle meningeal sinus
and sinus communicans were observed. A 53-year-old Caucasian woman was
referred for magnetic resonance imaging (MRI) investigation due to chronic headache.
On the MRI scan a solitary meningioma was observed. Finally MR 2D venography
revealed this extremely rare variant. (Folia Morphol 2011; 70, 4: 305–308
Semiclassical description of multiphoton processes
We analyze strong field atomic dynamics semiclassically, based on a full
time-dependent description with the Hermann-Kluk propagator. From the
properties of the exact classical trajectories, in particular the accumulation
of action in time, the prominent features of above threshold ionization (ATI)
and higher harmonic generation (HHG) are proven to be interference phenomena.
They are reproduced quantitatively in the semiclassical approximation.
Moreover, the behavior of the action of the classical trajectories supports the
so called strong field approximation which has been devised and postulated for
strong field dynamics.Comment: 10 pages, 11 figure
Nonsequential double ionization of helium
Published versio
Time-dependent natural orbitals and occupation numbers
We report equations of motion for the occupation numbers of natural spin
orbitals and show that adiabatic extensions of common functionals employed in
ground-state reduced-density-matrix-functional theory have the shortcoming of
leading always to occupation numbers which are independent of time. We
illustrate the exact time-dependence of the natural spin orbitals and
occupation numbers for the case of electron-ion scattering and for atoms in
strong laser fields. In the latter case, we observe strong variations of the
occupation numbers in time.Comment: 5 pages, 5 figure
The Myth of the Angry Atheist
Atheists are often portrayed in the media and elsewhere as angry individuals. Although atheists disagree with the pillar of many religions, namely the existence of a God, it may not necessarily be the case that they are angry individuals. The prevalence and accuracy of angry-atheist perceptions were examined in 7 studies with 1,677 participants from multiple institutions and locations in the United States. Studies 1–3 revealed that people believe atheists are angrier than believers, people in general, and other minority groups, both explicitly and implicitly. Studies 4–7 then examined the accuracy of these beliefs. Belief in God, state anger, and trait anger were assessed in multiple ways and contexts. None of these studies supported the idea that atheists are particularly angry individuals. Rather, these results support the idea that people believe atheists are angry individuals, but they do not appear to be angrier than other individuals in reality
A two-dimensional, two-electron model atom in a laser pulse: exact treatment, single active electron-analysis, time-dependent density functional theory, classical calculations, and non-sequential ionization
Owing to its numerical simplicity, a two-dimensional two-electron model atom,
with each electron moving in one direction, is an ideal system to study
non-perturbatively a fully correlated atom exposed to a laser field. Frequently
made assumptions, such as the ``single active electron''- approach and
calculational approximations, e.g. time dependent density functional theory or
(semi-) classical techniques, can be tested. In this paper we examine the
multiphoton short pulse-regime. We observe ``non-sequential'' ionization, i.e.\
double ionization at lower field strengths as expected from a sequential,
single active electron-point of view. Since we find non-sequential ionization
also in purely classical simulations, we are able to clarify the mechanism
behind this effect in terms of single particle trajectories. PACS Number(s):
32.80.RmComment: 10 pages, 16 figures (gzipped postscript), see also
http://www.physik.tu-darmstadt.de/tqe
Mesoscopic Phase Separation in Anisotropic Superconductors
General properties of anisotropic superconductors with mesoscopic phase
separation are analysed. The main conclusions are as follows: Mesoscopic phase
separation can be thermodynamically stable only in the presence of repulsive
Coulomb interactions. Phase separation enables the appearance of
superconductivity in a heterophase sample even if it were impossible in
pure-phase matter. Phase separation is crucial for the occurrence of
superconductivity in bad conductors. Critical temperature for a mixture of
pairing symmetries is higher than the critical temperature related to any pure
gap-wave symmetry of this mixture. In bad conductors, the critical temperature
as a function of the superconductivity fraction has a bell shape. Phase
separation makes the single-particle energy dispersion softer. For planar
structures phase separation suppresses d-wave superconductivity and enhances
s-wave superconductivity. These features are in agreement with experiments for
cuprates.Comment: Revtex file, 25 pages, 2 figure
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