75,022 research outputs found
Multiphoton inner-shell ionization of the carbon atom
We apply time-dependent R-matrix theory to study inner-shell ionization of C
atoms in ultra-short high-frequency light fields with a photon energy between
170 and 245 eV. At an intensity of 10 W/cm, ionization is dominated
by single-photon emission of a electron, with two-photon emission of a
1s electron accounting for about 2-3\% of all emission processes, and
two-photon emission of contributing about 0.5-1\%. Three-photon
emission of a 1s electron is estimated to contribute about 0.01-0.03\%. Around
a photon energy of 225 eV, two-photon emission of a 1s electron, leaving C
in either 1s2s2p or 1s2p is resonantly enhanced by intermediate
1s2s2p states. The results demonstrate the capability of time-dependent
R-matrix theory to describe inner-shell ionization processes including
rearrangement of the outer electrons.Comment: 7 pages, 2 figures, 2 table
Angular distributions in two-colour two-photon ionization of He
We present R-Matrix with time dependence (RMT) calculations for the
photoionization of helium irradiated by an EUV laser pulse and an overlapping
IR pulse with an emphasis on the anisotropy parameters of the sidebands
generated by the dressing laser field. We investigate how these parameters
depend on the amount of atomic structure included in the theoretical model for
two-photon ionization. To verify the accuracy of the RMT approach, our
theoretical results are compared with experiment.Comment: 8 pages, 4 figures, 1 tabl
Electron dynamics in the carbon atom induced by spin-orbit interaction
We use R-Matrix theory with Time dependence (RMT) to investigate multiphoton
ionization of ground-state atomic carbon with initial orbital magnetic quantum
number =0 and =1 at a laser wavelength of 390 nm and peak intensity
of 10 W cm. Significant differences in ionization yield and
ejected-electron momentum distribution are observed between the two values for
. We use our theoretical results to model how the spin-orbit interaction
affects electron emission along the laser polarization axis. Under the
assumption that an initial C atom is prepared at zero time delay with ,
the dynamics with respect to time delay of an ionizing probe pulse modelled
using RMT theory is found to be in good agreement with available experimental
data.Comment: 8 pages, 5 figure
Space-time discontinuous Galerkin method for the compressible Navier-Stokes equations on deforming meshes
An overview is given of a space-time discontinuous Galerkin finite element method for the compressible Navier-Stokes equations. This method is well suited for problems with moving (free) boundaries which require the use of deforming elements. In addition, due to the local discretization, the space-time discontinuous Galerkin method is well suited for mesh adaptation and parallel computing. The algorithm is demonstrated with computations of the unsteady \ud
ow field about a delta wing and a NACA0012 airfoil in rapid pitch up motion
Polarization fluctuations in vertical cavity surface emitting lasers: a key to the mechanism behind polarization stability
We investigate the effects of the electron-hole spin dynamics on the
polarization fluctuations in the light emitted from a vertical cavity surface
emitting laser (VCSEL). The Langevin equations are derived based on a rate
equation model including birefringence, dichroism, and two carrier density
pools seperately coupled to right and left circular polarization. The results
show that the carrier dynamics phase lock the polarization fluctuations to the
laser mode. This is clearly seen in the difference between fluctuations in
ellipticity and fluctuations in polarization direction. Seperate measurements
of the polarization fluctuations in ellipticity and in polarization direction
can therefore provide quantitative information on the non-linear contribution
of the carrier dynamics to polarization stability in VCSELs.Comment: 6 pages RevTex and 3 figures, to be published in Quantum and
Semiclassical Optics, minor changes to the discussion of timescale
Comment on "Large Difference in the Elastic Properties of fcc and hcp Hard-Sphere Crystals"
As is well known, hard-sphere crystals of the fcc and hcp type differ very
little in their thermodynamic properties. Nonetheless, recent computer
simulations by Pronk and Frenkel indicate that the elastic response to
mechanical deformation of the two types of crystal should be quite different.
By invoking a geometrical argument put forward by R. Martin some time ago, we
suggest that this is largely due to the different symmetries of the fcc and hcp
crystal structures. Indeed, we find that elastic constants obtained by means of
computer simulations for the fcc hard-sphere crystal can be mapped onto the
equivalent ones of the hcp crystal to very high accuracy. The same procedure
applied to density functional theoretical predictions for the elastic
properties of the fcc hard-sphere crystal also produces remarkably accurate
predictions for those of the hcp hard-sphere crystal.Comment: 7 pages, 5 figure
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Zugzwangs in chess studies
Van der Heijdenβs ENDGAME STUDY DATABASE IV, HHDBIV, is the definitive collection of 76,132 chess studies. The zugzwang position or zug, one in which the side to move would prefer not to, is a frequent theme in the literature of chess studies. In this third data-mining of HHDBIV, we report on the occurrence of sub-7-man zugs there as discovered by the use of CQL and Nalimov endgame tables (EGTs). We also mine those Zugzwang Studies in which a zug more significantly appears in both its White-to-move (wtm) and Black-to-move (btm) forms. We provide some illustrative and extreme examples of zugzwangs in studies
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Uniqueness in chess studies
Van der Heijdenβs ENDGAME STUDY DATABASE IV, HhdbIV, is the definitive collection of 76,132 chess studies. In each one, White is to achieve the stipulated goal, win or draw: study solutions should be essentially unique with minor alternatives at most. In this second note on the mining of the database, we use the definitive Nalimov endgame tables to benchmark Whiteβs moves in sub-7-man chess against this standard of uniqueness. Amongst goal-compatible mainline positions and goal-achieving moves, we identify the occurrence of absolutely unique moves and analyse the frequency and lengths of absolutely-unique-move sequences, AUMSs. We identify the occurrence of equi-optimal moves and suboptimal moves and refer to a defined method for classifying their significance
Malaria in Sri Lanka: Current knowledge on transmission and control
Malaria / Disease vectors / Waterborne diseases / Environmental effects / Public health / Economic impact / Social impact / Sri Lanka
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