8,703 research outputs found
Low-energy muon-transfer reaction from hydrogen isotopes to helium isotopes
Direct muon transfer in low-energy collisions of the muonic hydrogen H
and helium (He) is considered in a three-body quantum-mechanical
framework of coordinate-space integro-differential Faddeev-Hahn-type equations
within two- and six-state close coupling approximations. The final-state
Coulomb interaction is treated without any approximation employing appropriate
Coulomb waves in the final state. The present results agree reasonably well
with previous semiclassical calculations.Comment: 4 revtex4 page
Few-body semiclassical approach to nucleon transfer and emission reactions
A three-body semiclassical model is proposed to describe the nucleon transfer
and emission reactions in a heavy-ion collision. In this model the two heavy
particles, i.e. nuclear cores A and A, move along classical trajectories and
respectively, while the dynamics of the lighter neutron, n, is considered from
a quantum mechanical point of view. Here, are the nucleon masses and
are the Coulomb charges of the heavy nuclei (). A Faddeev-type
semiclassical formulation using realistic paired nuclear-nuclear potentials is
applied so that all three channels (elastic, rearrangement and break-up) are
described in an unified manner. In order to solve these time-dependent
equations the Faddeev components of the total three-body wave-function are
expanded in terms of the input and output channel target eigenfunctions. In the
special case when the nuclear cores are identical (A A) and the
two-level approximation in the expansion over target functions the
time-dependent semiclassical Faddeev equations are resolved in an explicit way.
To determine the realistic and trajectories of the
nuclear cores a self-consistent approach based on the Feynman path integral
theory is applied.Comment: 15 pages, 1 figur
Simulation technique for available bandwidth estimation
The paper proposes a method for measuring available bandwidth, based on
testing network packets of various sizes (Variable Packet Size method, VPS).
The boundaries of applicability of the model have been found, which are based
on the accuracy of measurements of packet delays, also we have derived a
formula of measuring the upper limit of bandwidth. The computer simulation has
been performed and relationship between the measurement error of available
bandwidth and the number of measurements has been found. Experimental
verification with the use of RIPE Test Box measuring system has shown that the
suggested method has advantages over existing measurement techniques. Pathload
utility has been chosen as an alternative technique of measurement, and to
ensure reliable results statistics by SNMP agent has been withdrawn directly
from the router
Ultracold collisions between two light indistinguishable diatomic molecules: elastic and rotational energy transfer in HD+HD
A close coupling quantum-mechanical calculation is performed for rotational
energy transfer in a HD+HD collision at very low energy, down to the ultracold
temperatures: K. A global six-dimensional H-H
potential energy surface is adopted from a previous work [Boothroyd {\it et
al.}, J. Chem. Phys., {\bf 116}, 666 (2002).] State-resolved integral cross
sections of different
quantum-mechanical rotational transitions in the HD
molecules and corresponding state-resolved thermal rate coefficients
have been computed. Additionally, for comparison,
H+H calculations for a few selected rotational transitions have also
been performed. The hydrogen and deuterated hydrogen molecules are treated as
rigid rotors in this work. A pronounced isotope effect is identified in the
cross sections of these collisions at low and ultracold temperatures.Comment: 9 pages, 9 figures. Accepted for publication in Physical Review
Coordinate-space Faddeev-Hahn-type approach to three-body charge transfer reactions involving exotic particles
Low-energy muon-transfer cross sections and rates in collisions of muonic
atoms with hydrogen isotopes are calculated using a six-state close-coupling
approximation to coordinate-space Faddeev-Hahn-type equations. In the muonic
case satisfactory results are obtained for all hydrogen isotopes and the
experimentaly observed strong isotopic dependence of transfer rates is also
reproduced. A comparison with results of other theoretical and available
experimental works is presented. The present model also leads to good transfer
cross sections in the well-understood problem of antihydrogen formation in
antiproton-positronium collision.Comment: 18 pages REVTeX, accepted for publication in Phys. Rev.
Determination of the temperature of a dense plasma from a spectral line shift
The method of maximum spectral line shift proposed by Bardocz, et al, (1966) was successfully applied in the diagnostics of dense plasmas produced by high power pulse discharges. It is pointed out that the effect of the shock wave pressure on the spectral line shift has to be taken into account in order to obtain accurate results with this method for high power discharges. A pressure dependent function was introduced in the expression given by those authors to provide the necessary correction
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