1,552 research outputs found
Seasonal Change of the Ozone Layer State over Yakutia
The ozone layer state in the stratosphere over Yakutia depending on the year
time is considered. It is shown that the layer thickness is maximum in
February-March (450 Dobson's units) and it is minimum in July-September (300 -
350 DU). Measurements indicate that the ozone layer thickness was significantly
decreased in the 1990's. A problem of change of ozone layer state is discussed.Comment: 3 pages, 2 figure
Momentum Analysis in Strong-field Double Ionization
We provide a basis for the laser intensity dependence of the momentum
distributions of electrons and ions arising from strong-field non-sequential
double ionization (NSDI) at intensities in the range . To do this we use a completely classical method introduced previously
\cite{ho-etal05}. Our calculated results reproduce the features of experimental
observations at different laser intensities and depend on just two distinct
categories of electon trajectories.Comment: 5 pages, 7 figure
Elliptical Trajectories in Nonsequential Double Ionization
Using a classical ensemble method, nonsequential double ionization is
predicted to exist with elliptical and circular polarization. Recollision is
found to be the underlying mechanism and it is only possible via elliptical
trajectories.Comment: Submitted to New Journal of Physic
Charged rho meson production in neutrino-induced reactions at E_nu = 10 GeV
The neutrinoproduction of charged mesons on nuclei and nucleons is
investigated for the first time at moderate energies ( 10
GeV), using the date obtained with SKAT bubble chamber. No strong nuclear
effects are observed in and production. The fractions of
charged and neutral pions originating from decays are obtained and
compared with higher energy data. From analysis of the obtained and available
data on and (892) neutrinoproduction, the strangeness
suppression factor in the quark string fragmentation is extracted: . Estimations are obtained for cross sections of quasiexclusive
single and coherent neutrinoproduction on nuclei. The
estimated coherent cross section = (0.29 cm is compatible with theoretical predictions.Comment: 7 pages, 6 figure
A study of the nuclear medium influence on transverse momentum of hadrons produced in deep inelastic neutrino scattering
The influence of nuclear effects on the transverse momentum
distributions of neutrinoproduced hadrons is investigated using the data
obtained with SKAT propane-freon bubble chamber irradiated in the neutrino beam
(with = 3-30 GeV) at Serpukhov accelerator. Dependences of of hadrons (more pronounced for the
positively charged ones) produced in the target fragmentation region at low
invariant mass of the hadronic system (2 4 GeV) or at low energies
transferred to the current quark (2 GeV). At higher or ,
no influence of nuclear effects on is observed. Measurement results
are compared with predictions of a simple model, incorporating secondary
intranuclear interactions of hadrons (with a formation length extracted from
the Lund fragmentation model), which qualitatively reproduces the main features
of the data.Comment: 23 pages, 7 figure
Inelastic scattering of broadband electron wave packets driven by an intense mid-infrared laser field
Intense, 100 fs laser pulses at 3.2 and 3.6 um are used to generate, by
multi-photon ionization, broadband wave packets with up to 400 eV of kinetic
energy and charge states up to Xe+6. The multiple ionization pathways are well
described by a white electron wave packet and field-free inelastic cross
sections, averaged over the intensity-dependent energy distribution for (e,ne)
electron impact ionization. The analysis also suggests a contribution from a 4d
core excitation in xenon
Classical and quantum-mechanical treatments of nonsequential double ionization with few-cycle laser pulses
We address nonsequential double ionization induced by strong, linearly
polarized laser fields of only a few cycles, considering a physical mechanism
in which the second electron is dislodged by the inelastic collision of the
first electron with its parent ion. The problem is treated classically, using
an ensemble model, and quantum-mechanically, within the strong-field and
uniform saddle-point approximations. In the latter case, the results are
interpreted in terms of "quantum orbits", which can be related to the
trajectories of a classical electron in an electric field. We obtain highly
asymmetric electron momentum distributions, which strongly depend on the
absolute phase, i.e., on the phase difference between the pulse envelope and
its carrier frequency. Around a particular value of this parameter, the
distributions shift from the region of positive to that of negative momenta, or
vice-versa, in a radical fashion. This behavior is investigated in detail for
several driving-field parameters, and provides a very efficient method for
measuring the absolute phase. Both models yield very similar distributions,
which share the same physical explanation. There exist, however, minor
discrepancies due to the fact that, beyond the region for which electron-impact
ionization is classically allowed, the yields from the quantum mechanical
computation decay exponentially, whereas their classical counterparts vanish.Comment: 12 pages revtex, 12 figures (eps files
Understanding the dynamics of photoionization-induced solitons in gas-filled hollow-core photonic crystal fibers
We present in detail our developed model [Saleh et al., Phys. Rev. Lett. 107]
that governs pulse propagation in hollow-core photonic crystal fibers filled by
an ionizing gas. By using perturbative methods, we find that the
photoionization process induces the opposite phenomenon of the well-known Raman
self-frequency red-shift of solitons in solid-core glass fibers, as was
recently experimentally demonstrated [Hoelzer et al., Phys. Rev. Lett. 107].
This process is only limited by ionization losses, and leads to a constant
acceleration of solitons in the time domain with a continuous blue-shift in the
frequency domain. By applying the Gagnon-B\'{e}langer gauge transformation,
multi-peak `inverted gravity-like' solitary waves are predicted. We also
demonstrate that the pulse dynamics shows the ejection of solitons during
propagation in such fibers, analogous to what happens in conventional
solid-core fibers. Moreover, unconventional long-range non-local interactions
between temporally distant solitons, unique of gas plasma systems, are
predicted and studied. Finally, the effects of higher-order dispersion
coefficients and the shock operator on the pulse dynamics are investigated,
showing that the resonant radiation in the UV [Joly et al., Phys. Rev. Lett.
106] can be improved via plasma formation.Comment: 9 pages, 10 figure
Relativistic photoelectron spectra in the ionization of atoms by elliptically polarized light
Relativistic tunnel ionization of atoms by intense, elliptically polarized
light is considered. The relativistic version of the Landau-Dykhne formula is
employed. The general analytical expression is obtained for the relativistic
photoelectron spectra. The most probable angle of electron emission, the
angular distribution near this angle, the position of the maximum and the width
of the energy spectrum are calculated. In the weak field limit we obtain the
familiar non-relativistic results. For the case of circular polarization our
analytical results are in agreement with recent derivations of Krainov [V.P.
Krainov, J. Phys. B, {\bf 32}, 1607 (1999)].Comment: 8 pages, 2 figures, accepted for publication in Journal of Physics
Absorption of Ultrashort Laser Pulses in Strongly Overdense Targets
We report on the first absorption experiments of sub-10 fs high-contrast
Ti:Sa laser pulses incident on solid targets. The very good contrast of the
laser pulse assures the formation of a very small pre-plasma and the pulse
interacts with the matter close to solid density. Experimental results indicate
that p-polarized laser pulses are absorbed up to 80 percent at 80 degrees
incidence angle. The simulation results of PSC PIC code clearly confirm the
observations and show that the collisionless absorption works efficiently in
steep density profiles
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