3,596 research outputs found
Two-particle Kapitza-Dirac diffraction
We extend the study of Kapitza-Dirac diffraction to the case of two-particle
systems. Due to the exchange effects the shape and visibility of the
two-particle detection patterns show important differences for identical and
distinguishable particles. We also identify a novel quantum statistics effect
present in momentum space for some values of the initial particle momenta,
which is associated with different numbers of photon absorptions compatible
with the final momenta.Comment: Minor changes with the published versio
Two-color interference stabilization of atoms
The effect of interference stabilization is shown to exist in a system of two
atomic levels coupled by a strong two-color laser field, the two frequencies of
which are close to a two-photon Raman-type resonance between the chosen levels,
with open channels of one-photon ionization from both of them. We suggest an
experiment, in which a rather significant (up to 90%) suppression of ionization
can take place and which demonstrates explicitly the interference origin of
stabilization. Specific calculations are made for H and He atoms and optimal
parameters of a two-color field are found. The physics of the effect and its
relation with such well-known phenomena as LICS and population trapping in a
three-level system are discussed.Comment: the paper includes 1 TeX file and 16 picture
Gaussian modeling and Schmidt modes of SPDS biphoton states
A double-Gaussian model and the Schmidt modes are found for the biphoton wave
function characterizing spontaneous parametric down-conversion with the
degenerate collinear phase-matching of the type I and with a pulsed pump. The
obtained results are valid for all durations of the pump pulses, short, long
and intermediately long
Computations of Three-Body Continuum Spectra
We formulate a method to solve the coordinate space Faddeev equations for
positive energies. The method employs hyperspherical coordinates and analytical
expressions for the effective potentials at large distances. Realistic
computations of the parameters of the resonances and the strength functions are
carried out for the Borromean halo nucleus 6He (n+n+alpha) for J = 0+, 0-, 1+,
1-, 2+,2-. PACS numbers: 21.45.+v, 11.80.Jy, 31.15.Ja, 21.60.GxComment: 10 pages, 3 postscript figures, LaTeX, epsf.sty, corrected misprints
in the caption of Fig.
Three-Body Halos in Two Dimensions
A method to study weakly bound three-body quantum systems in two dimensions
is formulated in coordinate space for short-range potentials. Occurrences of
spatially extended structures (halos) are investigated. Borromean systems are
shown to exist in two dimensions for a certain class of potentials. An
extensive numerical investigation shows that a weakly bound two-body state
gives rise to two weakly bound three-body states, a reminiscence of the Efimov
effect in three dimensions. The properties of these two states in the weak
binding limit turn out to be universal.
PACS number(s): 03.65.Ge, 21.45.+v, 31.15.Ja, 02.60NmComment: 9 pages, 2 postscript figures, LaTeX, epsf.st
Underwater measurements of muon intensity
Experimental measurements of cosmic ray muon intensity deep underwater aimed at determining a muon absorption curve are of considerable interest, as they allow to reproduce independently the muon energy spectrum at sea level. The comparison of the muon absorption curve in sea water with that in rock makes it possible to determine muon energy losses caused by nuclear interactions. The data available on muon absorption in water and that in rock are not equivalent. Underground measurements are numerous and have been carried out down to the depth of approx. 15km w.e., whereas underwater muon intensity have been measured twice and only down to approx. 3km deep
Extended symmetrical classical electrodynamics
In the present article, we discuss a modification of classical
electrodynamics in which ``ordinary'' point charges are absent. The modified
equations contain additional terms describing the induced charges and currents.
The densities of the induced charges and currents depend on the vector k and
the vectors of the electromagnetic field E and B. It is shown that the vectors
E and B can be defined in terms of two 4-potentials and the components of k are
the components of the 4-tensor of the third rank. The Lagrangian of modified
electrodynamics is defined. The conditions are derived at which only one
4-potential determines the behavior of the electromagnetic field. It is also
shown that static modified electrodynamics can describe the electromagnetic
field in the inner region of the electric monopole. In the outer region of the
electric monopole the electric field is governed by the Maxwell equations. It
follows from boundary conditions at the interface between the inner and outer
regions of the monopole that the vector k has a discrete spectrum. The electric
and magnetic fields, energy and angular momentum of the monopole are found for
different eigenvalues of k
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