931 research outputs found
The motion of a shock wave through a non-uniform one-dimensional medium in the case of arbitrary equation of state
The derivation of the equation of one-dimensional movement of a solitary
shock wave is given. This derivation shows, that the differential equation of
movement of a solitary plane shock wave in the channel with variable area, is
exact, if simplifying assumptions, made during derivation, are realized. But
these assumptions in plane geometry it is possible to realize only
approximately; situation with spherical and cylindrical shock waves is
opposite.Comment: 11 pages, 1 figure, 1 tabl
Is the Wannier threshold law for angular distribution in double photoionization of atoms true at practically attainable energies of ejected electrons?
We calculated ab initio the three-fold differential cross section of a double
single-photon Helium photoionization at equal energy sharing, and obtained from
one the Gaussian width parameter, describing the angular interelectron
correlations, for the total electrons energies range E from 0.1 eV to 100 eV.
The results are in excellent agreement with experimental data but indicate that
the Wannier threshold law for angular distribition is not correct at energies
attainable in modern experiments. It is shown that the Gaussian width parameter
dependence on energy is much better described by the modified threshold law,
obtained by Kazansky and Ostrovsky [J. Phys. B 26, 2231 (1993)]. Also, we
explored the Gaussian width parameter for a double photoionization of the
targets with the strongly asymmetrical initial state configuration: the atomic
Hydrogen negative ion and the Helium in the 2s1S and 3s1S excited states. We
found that the Gaussian width parameter dependence on the total ejected
electrons energy for this targets has a maximum at low energies. We show also
that the correlation parameter dependence on the interelectron angle for these
targets is essentially non-Gaussian and has a number of peaks equal to a number
of initial state radial nodes, that reveals the new abilities for the
qualitative analysis of electron structure.Comment: 13 pages, 8 figure
Multi-Component Gas-Dynamics and Turbulence
In the article, correct method for the kinetic Boltzmann equation asymptotic
solution is formulated, the Hilbert method and the Enskog error are considered.
The equations system of multi-component nonequilibrium gas-dynamics is derived,
that corresponds to the first order in the approximate method for solution of
the kinetic Boltzmann equation within the Struminskii approach. It is shown,
that velocity distribution functions, received by the proposed method and by
the Enskog method within the Enskog approach to solving of kinetic Boltzmann
equation for gas mixture, are equivalent to first infinitesimal order terms,
but, generally speaking, differ in the next order. An interpretation of
turbulent gas flow is proposed, as stratified to components gas flow, which is
described by the derived equations system of multi-component nonequilibrium
gas-dynamics.Comment: revtex, 31 pages in English, after "\end{document}" of english part
of tex-file original russian text is added; now we use more accurate
definition of the temperature, Enskog mistake is considered in more detail
Real-Space Renormalization Group (RSRG) Approach to Quantum Spin Lattice Systems
The paper describes an explicit variational modification of the standard RSRG
method and its application to quantum spin lattice systems. The modified
approach is applied to exactly solvable ITF, XX and isotropic Heisenberg
models. Better upper bounds for the systems' ground state energy are obtained
as compared to the standard RSRG approach.Comment: http://www.mff.cuni.cz/veda/konference/wds/proc/proc-contents.php?year=2011#phy
Solution of the Schr\"odinger equation using exterior complex scaling and fast Fourier transform
The split-operator pseudo-spectral method based on the fast Fourier transform
(SO-FFT) is a fast and accurate method for the numerical solution of the
time-dependent Schr\"odinger-like equations (TDSE). As well as other grid-based
approaches, SO-FFT encounters a problem of the unphysical reflection of the
wave function from the grid boundaries. Exterior complex scaling (ECS) is an
effective method widely applied for the suppression of the unphysical
reflection. However, SO-FFT and ECS have not been used together heretofore
because of the kinetic energy operator coordinate dependence that appears in
ECS applying. We propose an approach for the combining the ECS with SO-FFT for
the purpose of the solution of TDSE with outgoing-wave boundary conditions.
Also, we propose an effective ECS-friendly FFT-based preconditioner for the
solution of the stationary Schr\"odinger equation by means of the
preconditioned conjugate gradients method.Comment: 20 pages, 7 figure
Angular anisotropy of time delay in XUV/IR photoionization of H
We develop a novel technique for modeling of atomic and molecular ionization
in superposition of XUV and IR fields with characteristics typical for
attosecond streaking and RABBITT experiments. The method is based on solving
the time-dependent Schr\"odinger equation in the coordinate frame expanding
along with the photoelectron wave packet. The efficiency of the method is
demonstrated by calculating angular anisotropy of photoemission time delay of
the H ion in a field configuration of recent RABBITT experiments.Comment: 18 pages, 8 figure
The p-H symmetry breaking in dissociative ionization of H2 due to the molecular ion interaction with the ejected electron
We propose a novel mechanism of electron localization and molecular symmetry
breaking in dissociative photoionization of the H molecule. The Coulomb
field of the ejected electron can induce transition of the remaining H
ion from the gerade to the ungerade
electronic state when the nuclei in a bound
vibrational state are near the outer turning point. The superposition of this
process with a direct transition to vibrational continuum should produce a
non-gerade ionic state which results in observed asymmetry in the -H
ejection relative to the electron ejection direction at a small kinetic energy
release.Comment: 5 pages, 5 figure
Time-dependent calculations of transfer ionization by fast proton-helium collision in one-dimensional kinematics
We analyze a transfer ionization (TI) reaction in the fast proton-helium
collision by solving a time-dependent
Schr\"odinger equation (TDSE) under the classical projectile motion
approximation in one-dimensional kinematics. In addition, we construct various
time independent analogues of our model using lowest order perturbation theory
in the form of the Born series. By comparing various aspects of the TDSE and
the Born series calculations, we conclude that the recent discrepancies of
experimental and theoretical data may be attributed to deficiency of the Born
models used by other authors. We demonstrate that the correct Born series for
TI should include the momentum space overlap between the double ionization
amplitude and the wave function of the transferred electron.Comment: 10 pages, 6 figure
Time delay in XUV/IR photoionization of HO
We solve the time-dependent Schr\"odinger equation describing a water
molecule driven by a superposition of the XUV and IR pulses typical for a
RABBITT experiment. This solution is obtained by a combination of the
time-dependent coordinate scaling and the density functional theory with
self-interaction correction. Results of this solution are used to determine the
time delay in photoionization of the water and hydrogen molecules.Comment: 6 pages, 3 figures. arXiv admin note: text overlap with
arXiv:1604.0493
A full proof of universal inequalities for the distribution function of the binomial law
We present a new form and a short full proof of explicit two-sided estimates
for the distribution function F_{n,p}(x) of the binomial law from the paper
published by D.Alfers and H.Dinges in 1984. These inequalities are universal
(valid for all binomial distribution and all values of argument) and exact
(namely, the upper bound for F_{n,p}(k) is the lower bound for F_{n,p}(k+1)).
By means of such estimates it is possible to bound any quantile of the binomial
law by 2 subsequent integers.Comment: 7 pages; to be published in "Teorija verojatnostei i ee primenenija"
(in Rissian
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