ON DARBOUX-BÄCKLUND TRANSFORMATION AND POSITON TYPE SOLUTION OF
COUPLED NONLINEAR OPTICAL WAVES
D.C. Sen and A.R. ChowdhuryHigh Energy Physics Division,
Department of
Physics, Jadavpur University Calcutta-700032, India
Received: April 8, 1999; revised version September 23, 1999; in final form
February 18, 2000
A Darboux-Bäcklund transformation is used to obtain a positon
type
solution of the nonlinear equations describing the propagation of
coupled
nonlinear optical pulses.This form of the positon solution is then
compared
with that obtained by the special limiting procedure applied to a
two-soliton
solution. It is observed that though the algebraic form of the two
solutions
is different yet both of these have singularities and the position of
the
singularities remains on the similar curve in the (x,t) plane. We also
depict
the form of these solutions graphically. Finally, it may be added that
the
method of Darboux-Bäcklund transformation is convenient for
generating
more than one-positon solution.
PACS numbers: 02.30.+g, 52.35.Sb, 52.35.Mw
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TIME EVOLUTION OF SU(1,1) COHERENT STATES
J. ZalesnyInstitute of Physics, Technical University of Szczecin
Al.
Piastów 48, 70-310 Szczecin, Poland
Received: August 5, 1999; revised version January 28, 2000; in final form
July
28, 2000
Mathematical aspects of the SU(1,1) group parameter xi dynamics
governed by Hamiltonians exhibiting some special types of time
dependence was
presented on an elementary level from the point of view of the Möbius
transformation of complex plane. The trajectories of xi in continuous
and
mappings in discrete dynamics are considered. Some simple examples were
examined. Analytical considerations and numerical results were
given.
PACS numbers: 03.65.Fd, 02.20.Sv
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THEORY OF CRITICAL SOUND ATTENUATION IN ISING-TYPE MAGNETS
A. PawlakInstitute of Physics, A. Mickiewicz University
Umultowska
85, 61-614 Poznań, Poland
Received: May 30, 2000
The critical behaviour of sound attenuation has been studied in an
elastically isotropic Ising system above the critical point on the basis
of a
complete stochastic model including both spin-energy and lattice-energy
modes
linearly coupled to the longitudinal sound mode. The effect of
spin-lattice
relaxation on the ultrasonic attenuation is investigated. The crossover
between Kawasaki behaviour and Murata-Iro-Schwabl behaviour is studied
as
dependent on the values of ultrasonic frequency, reduced temperature,
relaxation times, etc. A new high-frequency regime is discussed in the
magnetic systems. This new regime corresponds to an adiabatic sound
propagation and is very similar to the ones in binary mixture and liquid
helium. A new frequency-dependent specific heat being the harmonic
average of
the bare lattice and critical spin specific heats is introduced. It was
shown
that such specific heat describes the process of equilibration between
spin
and lattice subsystems and includes the most important features of
critical
sound attenuation.
PACS numbers: 05.70.Jk, 62.65.+k
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EXCHANGE CONTRIBUTIONS TO SPIN POLARIZATION IN LOW-ENERGY ELECTRON
SCATTERING FROM Xe AND Hg
J.E. Sienkiewicza, S. Fritzscheb
and P. Sytyaa Department of
Applied Physics and Mathematics Technical University of Gdańsk, G.
Narutowicza 11/12, 80-952 Gdańsk, Poland,^bFachbereich Physik,
Universität Kassel, 34132 Kassel, Germany
Received: March 14, 2000
The contribution of exchange interactions is investigated for spin
polarization of electrons which are scattered elastically from xenon and
mercury at the energy of 1.5 eV. We find that electron exchange between
the
bound-state and the scattered electron gives rise to a substantial spin
polarization in both cases.
PACS numbers: 34.80.Bm, 31.30.Jv
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ON EFFICIENT FIELD ENERGY CONVERSION IN NON-PHASE-MATCHED FREQUENCY
DOUBLING PROCESS
W. Jedaa and A. Zagörskiba Systems
Research Institute, Polish Academy of Sciences Newelska 6, 01-447 Warszawa,
Poland,
b Faculty of
Physics, Warsaw University of Technology Koszykowa 75, 00-662 Warszawa,
Poland
Received: March 14, 2000
In the paper the efficiency of the light energy conversion from
the
fundamental wave into its second harmonics is analysed. A standard model
of
three waves mixing in media without centre of symmetry was applied. It
was
shown that the full conversion of energy is possible if an appropriate
phase
difference exists and provided that at least a minimal energy of the
second
wave is present on the input. The results are expressed both by
analytical
formulas and a phase space reconstruction. A simple experimental setup
to
enhance the second harmonics is proposed.
PACS numbers: 42.65.Hw, 42.65.Ky
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STUDY OF SPONTANEOUS POLARISATION AND PYROELECTRIC MODULUS FOR THE
TRIGLYCINE SULPHATE CRYSTALS DOPED BY CHROMIUM IONS
J. Dziedzic and B. StoleckiInstitute of Physics, Technical
University
of Wroclaw Wybrzeze Wyspiańskiego 27, 53-370 Wroclaw, Poland
Received: January 3, 2000; revised version April 7, 2000
The temperature dependencies of a spontaneous polarisation,
Ps, and
pyroelectric modulus, gamma, at different electric field intensities
were
investigated for the triglycine sulphate crystals doped with the Cr3+
chromium ions. On the base of thermodynamic theory the temperature
dependencies of Ps and gamma at different electric field
intensities
were estimated. The coefficients of the expansion of the thermodynamic
potential were determined. The experimental results were compared with
those
obtained according to the thermodynamic theory.
PACS numbers: 64.70.Kb
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DILATOMETRIC INVESTIGATIONS OF OVERCRITICAL BEHAVIOUR IN
[N(C2H5)4]2CuCl4
CRYSTALS
R. Poprawskia, A. Liberb
and E. Malekaa Institute of Physics,
Wroclaw University of Technology Wybrzeze Wyspiańskiego 27, 50-370
Wroclaw, Poland,
b Computer Science Department, Wroc/law University of
Technology Wybrzeze Wyspiańskiego 27, 50-370 Wroclaw, Poland
Received: February 23, 2000
The results of experimental investigation of thermal expansion
of [N(C2H5)4]2CuCl4
crystals in a wide temperature range
are presented. The anomaly of thermal deformation typical of first order
phase transition at 258 K and additional continuous anomaly at 195 K
were
observed. It was shown that low temperature anomalies of physical
properties
of [N(C2H5)4]2CuCl4
crystals can be described as
overcritical trace of isomorphous phase transitions. Results of
numerical
analysis of phenomenological model of improper ferroelastic exhibiting
isomorphous phase transitions are presented and compared with
experimentally
determined temperature dependencies of spontaneous deformation of
[N(C2H5)4]2Cu Cl4 crystals.
PACS numbers: 61.68.+n
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MOLECULAR DYNAMICS OF 4-(trans-4'-n-HEPTYLCYCLOHEXYL)-
ISOTHIOCYANATOBENZENE STUDIED WITH DIELECTRIC RELAXATION SPECTROSCOPY
D. Baumana, G. Czechowskib, J. Jadzynb,
C. Legrandc and
R. Doualica Faculty of Technical Physics,
Poznań University of
Technology
Piotrowo 3, 60-965 Poznań, Poland,
b Institute of Molecular Physics,
Polish
Academy of Sciences Smoluchowskiego 17, 60-179 Poznań,
Poland,
c Université
du Littoral - Cote d'Opale, LEMCEL, BP 689, 62-228 Calais, France
Received: May 23, 2000
Dielectric relaxation study was carried out for the nematic and
isotropic phases of 4-(trans-4'-n-
heptylcyclohexyl)isothiocyanatobenzene in
the frequency range from 100 kHz to 1 GHz. In the nematic phase two
relaxation processes were recorded for the electric permittivity
component
measured parallel to the molecular orientation (director n) and
three
relaxation processes - for the perpendicular permittivity component.
The
strength of the nematic potential and the nematic order parameter were
estimated.
PACS numbers: 64.70.Md, 77.84.Nh, 77.22.Gm
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CALCULATIONS OF EuTe MAGNETIC PHASE DIAGRAM FOR EXTERNAL PRESSURE
A. Radomska and T. BalcerzakSolid State Physics Department,
University
of Lódz Pomorska 149/153, 90-236 Lódz, Poland
Received: February 23, 2000; in final form April 28, 2000
The magnetic phase diagram of europium telluride, EuTe, under
external
high pressure is theoretically investigated. Besides nearest-neighbour
and
next-nearest-neighbour exchange interactions, the long-range dipolar and
biquadratic interactions are taken into account. The functional
dependences
of these interactions on the lattice constant are proposed. The
calculated
Néel and Curie temperatures are compared with the experimental data.
Two
new phases, antiferrimagnetic and ferrimagnetic, have been found at a
high
pressure and low temperatures.
PACS numbers: 75.10.-b, 75.50.Ee, 75.50.Pp
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ELECTRICAL CONDUCTIVITY AND THERMOELECTRIC POWER OF
a-Se80-xGa20Tex (x=3D0,5,10,15 AND 20) THIN FILMS
Zishan H. Khana, M. Zulfequarb,
M. Ilyasb and M. Husainba Department
of Applied Sciences & Humanities,Faculty of
Engineering
& Technology Jamia Millia Islamia, New Delhi-110025,
India,
b Department of
Physics, Jamia Millia Islamia, New Delhi-110025 India
Received: February 28, 2000; revised version May 15, 2000
The dc conductivity and thermoelectric power of
a-Se80-xGa20Tex
(x=3D0,5, 10,15 and 20) thin films were
reported in the present work. The free charge carrier concentration was
calculated with the help of dc conductivity and thermoelectric power
measurements. The calculated values of free charge carrier concentration
were
used to evaluate the free charge carrier mobility from which grain
boundary
potential was evaluated. The results are interpreted in terms of small
polaron hopping, the structure of Se-Te and the grain boundary potential
barrier.
PACS numbers: 73.61.Jc
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DOMAIN PATTERN EVOLUTION IN POLARIZATION REVERSAL OF TELLURIC ACID
AMMONIUM PHOSPHATE CRYSTALS
K. Matyjaseka and Z. Czaplaba Institute
of Physics, Technical
University of Szczecin Al. Piastów 48/49, 70-311 Szczecin, Poland,
b Institute of Experimental Physics, University of Wroclaw
Pl. M. Borna 9,
50-204 Wroclaw, Poland
Received: March 14, 2000; in final form April 20, 2000
The domain nucleation and growth during switching process in
telluric
acid ammonium phosphate crystals has been investigated by nematic liquid
crystal decoration technique. The domain configuration arising during
polarization reversal has been discussed, considering that the type of
nucleation is the controlling factor in the propagation of the domain
walls.
PACS numbers: 77.80.Dj
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BINDING ENERGY OF A BOUND POLARON IN A QUANTUM WELL WIRE
M. Bouhassounea, R. Charroura,
M. Fliyoub, D. Briaa and A.
Nougaouiaa Laboratoire de Dynamique et d'Optique
des Matériaux,
Faculté des Sciences Université Mohamed 1er, Oujda,
Morocco,
b Equipe de
Physique du Solide, ENS, B.P. 5206 Benssouda, Fčs, Morocco
Received: April 11, 2000
Theoretical study of the binding energies of an off-center donor
hydrogenic impurity in a cylindrical quantum well wires semiconductor is
presented. Calculations are performed in the framework of the effective
mass
approximation using the variational approach. We describe the effect of
the
quantum confinement by an infinitely deep potential well and we take
into
consideration the interaction between the charge carrier (electron and
ion)
and the optical phonons (confined longitudinal optical and surface
optical).
Our results show that the impurity binding energy depends strongly on
the
spatial confinement, the impurity position and the polaronic
corrections.
PACS numbers: 71.38.+i, 73.20.Dx, 73.20.Hb, 73.20.Fz
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ANALYTICAL BAND MODEL IN MONTE CARLO SIMULATION OF ELECTRIC
TRANSPORT IN
ZnS THIN FILM ELECTROLUMINESCENT DEVICES
H. Zhao, Y. Wang and X. XuInstitute of Optoelectronic Technology,
Northern Jiaotong University Beijing 100044, China
Received: May 8, 2000
In this paper, an analytical band model is introduced in Monte
Carlo
simulation of electric transport process in thin film electroluminescent
devices. The band structure of ZnS calculated from the empirical
pseudopotential method is fitted by using polynomials. The density of
states
and scattering rates are also calculated from these polynomials. Based
on
these results, the electric transport process in ZnS-type thin film
electroluminescent devices is simulated through the Monte Carlo method.
By
comparison with others, this model is as fast as the nonparabolic model
and
as accurate as the full band model. Furthermore, the influence of the
band
model on the simulation results is also investigated. We show that the
dispersion relation and density of states are all important in the
simulation.
PACS numbers: 78.60.-b, 72.20.-i
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PROTON AND DEUTERON RELAXATION STUDY OF MOLECULAR DYNAMICS IN
LYSOZYME SOLUTIONS
J.F. Kakulea, W.P. Weglarzb,
R.K. Shenoyc, A.R. Sharpa and H.
Peemoellerca Department of Physics, University
of New Brunswick,
Fredericton New Brunswick, E3B 5A3, Canada,
b H. Niewodniczański
Institute of
Nuclear Physics, Kraków, Poland,
c Department of Physics, University of
Waterloo, Waterloo, Ontario, N2L 3G1, Canada
Received: August 23, 1999; revised version May 15, 2000
A nuclear magnetic resonance spin-lattice relaxation dispersion
study
of the relaxation of several magnetization components in both natural
and deuterated lysozyme solutions was undertaken at 20°C. Proton and
deuteron resonances were employed. The two-dimensional time evolution of
the
magnetization and the spin-spin relaxation were analyzed. In addition,
an
isotopic dilution study was performed at 5 and 30.6MHz. The results
indicate
that the water proton spin-lattice relaxation rate which arises from
intermolecular relaxation between the water protons and the lysozyme
protons
represents a relatively strong relaxation mechanism. A model for the
dynamics
of the water molecules, consistent with the proton and deuteron
dispersions
as well as with the isotopic dilution results, is presented.
PACS numbers: 87.15.-v,
76.60.-k,
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LIQUID PHASE CONTAINED IN POROUS ROCK AS OBSERVED BY PROTON MAGNETIC
RELAXATION
H. Harańczyka and A.
Wójcikba Institute of Physics,
Jagiellonian
University, Reymonta 4, 30-059 Cracow, Poland,
b Faculty of Geology,
Geophysics and Environmental Protection, Dept. of Geophysics Academy of
Mining and Metalurgy, Cracow, Poland
Received: February 14, 2000; revised version April 28, 2000
High power proton relaxometry was applied to investigate the
liquid
phase contained in porous rock. Proton free induction decays and
spin-lattice relaxation times allowed us to investigate the pore
distribution and the contribution of mobile and of immobilized liquid.
The
differences in pore distributions in oil-containing limestone and in
Weglowicki sandstone were found. The fractal exponent for pore
distribution
in Weglowicki sandstone was fitted using both stretched exponential and
modified stretched exponential models. The results of both approaches
are compared.
PACS numbers: 81.05.Rm, 76.60.Es
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ERRATUM
W. Schmidt, Exchange Stiffness Parameter and Magnetization in Pseudopotential Calculations,
Acta Phys. Pol. A 97, 967 (2000).
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