3,713 research outputs found
Quantum kinetic theory of shift current electron pumping in semiconductors
We develop a theory of laser beam generation of shift currents in
non-centrosymmetric semiconductors. The currents originate when the excited
electrons transfer between different bands or scatter inside these bands, and
asymmetrically shift their centers of mass in elementary cells. Quantum kinetic
equations for hot-carrier distributions and expressions for the induced
currents are derived by nonequilibrium Green functions. In applications, we
simplify the approach to the Boltzmann limit and use it to model laser-excited
GaAs in the presence of LO phonon scattering. The shift currents are calculated
in a steady-state regime.Comment: 23 pages, 5 figures (Latex
Search for the Cryptoexotic Member of the Baryon Antidecuplet 1/2+ in the Reactions pi- p --> pi- p and pi- p --> K L
The main goal of this proposal is the search for a narrow cryptoexotic
nucleon resonance by scanning of the pi- p system invariant mass in the region
(1610-1770) MeV with the detection of pi- p and K Lambda decays. The scan is
supposed to be done by the variation of the incident pi- momentum and its
measurement with the accuracy of up to +-0.1% (better than 1 MeV in terms of
the invariant mass in the whole energy range) with a set of proportional
chambers located in the first focus of the magnetooptical channel. High
sensitivity of the method to the resonance under search is shown. The secondary
particles scattered from a liquid hydrogen target are detected by sets of the
wire drift chambers equipped with modern electronics. The time scale of the
project is about 3 years. The budget estimate including manpower, the apparatus
and operation cost, is about 40 million rubles. The beam time required is (4-6)
two week runs on "high" (10 GeV/c) flattop of the ITEP proton synchrotron.Comment: 16 pages, 10 figures. v2: an acknowledge adde
Backward asymmetry measurements in the elastic pion-proton scattering at resonance energies
The asymmetry parameter P was measured for the elastic pion-proton scattering
in the very backward angular region of theta_cm ~ 150-170^o at several pion
beam energies in the invariant mass range containing most of the pion-proton
resonances.
The general goal of the experimental program was to provide new data for
partial wave analyses in order to resolve their uncertainties in the baryon
resonance region to allow the unambiguous baryon spectrum reconstructions.
Until recently the parameter P was not measured in the examined domain that
might be explained by the extremely low cross section. At the same time the
predictions of various partial wave analyses are far from agreement in some
kinematic areas and specifically those areas were chosen for the measurements
where the disagreement is most pronouncing.
The experiment was performed at the ITEP U-10 proton synchrotron, Moscow, by
the ITEP-PNPI collaboration in the latest 5 years.Comment: 6 pages, 5 figures. to be submitted to the European Physical Journa
Luminescent properties of Bi-doped polycrystalline KAlCl4
We observed an intensive near-infrared luminescence in Bi-doped KAlCl4
polycrystalline material. Luminescence dependence on the excitation wavelength
and temperature of the sample was studied. Our experimental results allow
asserting that the luminescence peaked near 1 um belongs solely to Bi+ ion
which isomorphically substitutes potassium in the crystal. It was also
demonstrated that Bi+ luminescence features strongly depend on the local ion
surroundings
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