426 research outputs found
Cross-relaxation and phonon bottleneck effects on magnetization dynamics in LiYF4:Ho3+
Frequency and dc magnetic field dependences of dynamic susceptibility in
diluted paramagnets LiYF:Ho have been measured at liquid helium
temperatures in the ac and dc magnetic fields parallel to the symmetry axis of
a tetragonal crystal lattice. Experimental data are analyzed in the framework
of microscopic theory of relaxation rates in the manifold of 24
electron-nuclear sublevels of the lowest non-Kramers doublet and the first
excited singlet in the Ho ground multiplet split by the crystal
field of S symmetry. The one-phonon transition probabilities were computed
using electron-phonon coupling constants calculated in the framework of
exchange charge model and were checked by optical piezospectroscopic
measurements. The specific features observed in field dependences of the in-
and out-of-phase susceptibilities (humps and dips, respectively) at the
crossings (anti-crossings) of the electron-nuclear sublevels are well
reproduced by simulations when the phonon bottleneck effect and the cross-spin
relaxation are taken into account
High energy inelastic electron hadron scattering, in peripheral kinematics. Sum rules for hadron form factors
Relations between differential cross section for inelastic scattering of
electrons on hadrons and hadron form factors (sum rules) are derived on the
basis of analytical properties of heavy photon forward Compton scattering on
hadrons. Sum rules relating the slope of form-factors at zero momentum transfer
and anomalous magnetic moments of hadrons with some integrals on
photo-production on a hadrons is obtained as well. To provide the convergence
of these integrals we construct differences of individual sum rules for
different hadrons. Universal interaction of Pomeron with nucleons is assumed.
We derive the explicit formulae for processes of electro-production on proton
and light isobar nuclei. Sudakov's parametrization of momenta, for peripheral
kinematics relevant here, is used. The light-cone form of differential cross
sections is also discussed. The accuracy of sum rules estimated in frames of
point-like hadrons and it is shown to be at the level of precision achievable
by experiments. Suggestions and predictions for future experiments are also
given.Comment: 18 pages, 5 figure
Erforschung von biokompatiblen und korrosionsbestandigen Beschichtungen, die auf Titanlegierung Vt6 durch Elektroerosivemetallbearbeitung aufgetragen werden
В статье рассмотрены фазовый и химико-элементный составы покрытия для ортопедии и дентальной медицины, нанесенного на титановый сплав ВТ6методом электроискровой обработки металлов с целью предотвращения попадания с поверхности сплава в организм человека химических элементов, оказывающих токсическое воздействие
Possible Method for Measuring the Proton Form Factors in Processes with and without Proton Spin Flip
The ratio of the squares of the electric and magnetic proton form factors is
shown to be proportional to the ratio of the cross sections for the elastic
scattering of an unpolarized electron on a partially polarized proton with and
without proton spin flip. The initial proton at rest should be polarized along
the direction of the motion of the final proton. Similar results are valid for
both radiative scattering and the photoproduction of pairs on a proton in
the Bethe--Heitler kinematics. When the initial proton is fully polarized in
the direction of the motion of the final proton, the cross section for the process, as well as for the and processes, without (with) proton spin flip is expressed only in terms of
the square of the electric (magnetic) proton form factor. Such an experiment on
the measurement of the cross sections without and with proton spin flip would
make it possible to acquire new independent data on the behavior of
and , which are necessary for resolving the
contradictions appearing after the experiment of the JLab collaboration on the
measurement of the proton form factors with the method of polarization transfer
from the initial electron to the final proton.Comment: 7 pages, revtex
High-level consultation meeting on Eurasian Economic Integration. IIASA project “Challenges and Opportunities of Economic Integration within a Wider European and Eurasian Space” Workshop Report
High-level consultation meeting on Eurasian Economic Integration. IIASA project “Challenges and Opportunities of Economic Integration within a Wider European and Eurasian Space” Executive Summary
Polarized triplet production by circularly polarized photons
A process of the pair production by a circularly polarized photon in the
field of unpolarized atomic electron has been considered in the
Weizaecker-Williams approximation. The degree of longitudinal polarization of
positron and electron has been calculated. An exclusive cross-section as well
as a spectral distribution are obtained. We estimate the accuracy of our
calculations at the level of a few percent. We show the identity of the
positron polarization for considered process and for process of pair production
in the screened Coulomb field of nucleus.Comment: 9 pages, 3 picture
Convergence of the Magnus series
The Magnus series is an infinite series which arises in the study of linear
ordinary differential equations. If the series converges, then the matrix
exponential of the sum equals the fundamental solution of the differential
equation. The question considered in this paper is: When does the series
converge? The main result establishes a sufficient condition for convergence,
which improves on several earlier results.Comment: 11 pages; v2: added justification for conjecture, minor
clarifications and correction
One-dimensional Model of a Gamma Klystron
A new scheme for amplification of coherent gamma rays is proposed. The key
elements are crystalline undulators - single crystals with periodically bent
crystallographic planes exposed to a high energy beam of charged particles
undergoing channeling inside the crystals. The scheme consists of two such
crystals separated by a vacuum gap. The beam passes the crystals successively.
The particles perform undulator motion inside the crystals following the
periodic shape of the crystallographic planes. Gamma rays passing the crystals
parallel to the beam get amplified due to interaction with the particles inside
the crystals. The term `gamma klystron' is proposed for the scheme because its
operational principles are similar to those of the optical klystron. A more
simple one-crystal scheme is considered as well for the sake of comparison. It
is shown that the gamma ray amplification in the klystron scheme can be reached
at considerably lower particle densities than in the one-crystal scheme,
provided that the gap between the crystals is sufficiently large.Comment: RevTeX4, 22 pages, 4 figure
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