Lotfi Zaki

The dynamics of an electron in the fields associated
with a TE electromagnetic wave propagating inside a circular
waveguide is analytically studied. The motion of this electron along
the axis of the waveguide is investigated in the existence of a
helical magnet (in which the field is perpendicular to the axis of
the waveguide and rotating as a function of position along the
magnet). It is shown that it can be accelerated due to its interaction
with polarized fields of microwave radiation propagating along
the waveguide. The fields for the lowest order TE11 modes and
the deflection angle of electron trajectory, due to these fields, are
obtained. Also, an expression of the acceleration gradient of the
electron and its energy gain are evaluated for different intensities
and frequencies of the microwave.

In this work, we study the effect of concentration,
host medium, PH and phase states on the fluorescence
emission from the laser dye Rhodamine B pumped by UV
laser as exited source. The polymethylmethacrylate PMMA is
used as a host medium in case of solid phase samples while,
ethanol and Tetrahydrofuran (THF) are used in case of a liquid
one. Laser Induced Fluorescence (LIF) technique was used to
study the fluorescence properties of both cases of liquid and
thin film solid-state samples. In addition, the Dual Thermal
Lens (DTL) technique was used to study the quantum yield of
these samples. The concentrations of Rhodamine B in ethanol
as solvent between 2×10−2 M and 5×10−6 M were studied.
The maximum fluorescence emission is observed at concentration
of Rhodamine B C=3×10−4 M. Comparison studies
were investigated for different host medium such as ethanol,
THF, PMMA in liquid phase state and PMMA in solid phase
state. The measurements revealed that, the behavior of both
phases state was analogous. Rhodamine B/PMMA thin film
sample by ratio of 4:1 and thickness 0.12 mm was found to
have the best photostability sample with a quantum yield
about ≈0.82.

A new oxidation technique of high temperature superconducting copper oxides has been invented. The oxidation is performed in a low
pressure oxygen plasma generated by a microwave. X-ray and the low temperature alternating current magnetic susceptibility have been
used to explore the effect of the oxidation on the superconducting behavior. Also, the measured infrared spectra reveal good dependence
of the two copper–oxygen populations. © 2002 Elsevier Science B.V. All rights reserved.