COHERENT POPULATION TRAPPING
IN OPEN AND CLOSED SYSTEMS
L. WindholzInstitut für Experimentalphysik, Technische
Universität Graz
Petersgasse 16, 8010 Graz, Austria
Received: July 7, 1999
In the present paper, an overview on work concerning coherent
population trapping within the hyperfine manifold of the sodium D1-line
is given. Besides manifestation of coherent population trapping for different
Lambda-schemes, also phase dependent processes in closed contour
systems (four-level double Lambda-schemes) are discussed,
including the case of phase dependent electromagnetically induced
transparency.
PACS numbers: 32.80.-t, 42.50.-p
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INFLUENCE OF EXCITATION PROCESSES
ON THE SHAPE OF ARGON AND NEON LINES
A. Bielski, R. Ciurylo, D. Lisak
and R.S. TrawińskiInstitute of Physics, Nicholas Copernicus
University
Grudziadzka 5/7, 87-100 Toruń, Poland
Received: September 21, 1999; revised version November 30, 1999
Shapes of self-broadened argon lines 687.1 nm (4d5-2p10),
703.0 nm (3s5-2p9), 750.3 nm
(2p1-1s2) as well as the neon line
748.8 nm (3d3-2p10) emitted from glow discharges at low pressures
were
analysed using a Fabry Perot interferometer. We showed that the
dissociative recombination of Ar+2 (or Ne+2)
molecular ions which gives
rise to the density of non-thermalized atoms, may be regarded as the main
process responsible for the distortion of the profiles of the above lines.
The distorted profiles were analysed as superposition of the Ballik profile
for thermalized atoms and the modified Ballik profile for non-thermalized
atoms. The Lorentzian and Gaussian widths as well as relative densities of
non-thermalized and thermalized atoms were
determined.
PACS numbers: 32.70.-n, 33.70.-w, 34.20.-b
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NORMAL MODE ANALYSIS OF VIBRATIONS
OF JET-COOLED ACRIDINE DIMER
I. Deperasińska and J. ProchorowInstitute of Physics,
Polish Academy of Sciences
Al. Lotników 32/46,
02-668 Warsaw, Poland
Received: November 19, 1999
The analysis of normal modes of vibrations was performed for acridine
dimer, which has been recently observed and identified by laser-induced
emission spectroscopy under conditions of jet-cooling in a supersonic helium
expansion. The frequencies and the forms of normal vibrations, computed with
the use of the semi-empirical PM3 method are classifying all vibrations of
acridine dimer into two distinct categories of inter- and intramolecular
vibrations. There are six low-frequency intermolecular normal vibrations
which are characterizing relative movements of two acridine moieties in the
dimer and at least two of them have vibrational frequencies which are close
to the frequencies of vibronic bands observed in the fluorescence excitation
spectrum of the dimer. The intramolecular normal vibrations of the dimer
very
strictly correspond to the normal vibrations of acridine molecule (with a
minor modification of the vibrational frequencies due to the splitting in
the
dimer). Furthermore, the intramolecular vibrations of acridine dimer, as
well
as the vibrations of acridine molecule are in good agreement with available
experimental data (either IR and Raman spectra of acridine or fluorescence
excitation spectrum of acridine dimer in supersonic jet). The results of the
present analysis are very clearly supporting the previous conclusions
concerning the ground-state equilibrium structure of acridine dimer formed
under jet-cooling conditions.
PACS numbers: 33.20.Tp
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MODELLING OF BLUE WAVELENGTH PRASEODYMIUM WAVEGUIDE LASERS
M. Malinowskia, A. Mossakowska-Wyszyńskaa,
R. Piramidowicza,
P. Szczepańskia, A. Tyszka-Zawadzkaa,
Z. Frukaczb and I. Prackaba Institute of
Microelectronics and Optoelectronics P.W.
Koszykowa 75,
00-662 Warsaw, Poland
b Institute of Electronic Materials Technology,
Wólczyńska 133, 01-919 Warsaw, Poland
Received: October 13, 1999
Emission and absorption spectra, lifetimes, and branching ratios in
the
blue spectral region have been experimentally determined for numerous oxide,
fluoride and phosphate materials doped with Pr3+ ions. The emission
cross-sections have been evaluated using the principle of reciprocity. A
theoretical model allowing a prediction of the blue lasing characteristics
of
the praseodymium activated waveguide structures has been developed and
employed to the investigated
materials.
PACS numbers: 42.70.Hj, 78.20.-e, 78.55.Hx
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PHYSICAL STUDIES
OF CYCLOHEXANE DERIVATIVES
Y.N. Murthya, M.V. Ramanaiahb
and V.R. Murthyca Department
of Physics, S.S.B.N. College, Anantapur - 515 001, India
b
Dept. of Physics, S.D.G.S. College, Hindupur - 515 202, India
c Dept. of
Physics, S.K. University, Anantapur - 515 003, India
Received: July 7, 1999; revised version November 15, 1999
Mean molecular polarizabilities, polarizability anisotropies and order
parameters of two homologous series of cyclohexane derivatives
namely trans-4-alkyl cyclohexyl 4' -cyanophenyl ester and
trans-4-alkyl cyclohexyl 4'-n -pentyloxy phenyl ester are
evaluated
using molecular vibration approach. The variation of polarizability and
polarizability anisotropy with a number of carbon atoms in the alkyl chain
is studied. In addition, the dependence of order parameter on temperature is
reported and discussed.
PACS numbers: 61.30.-v
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MOLECULAR DYNAMICS OF n-p -(ETHOXYBENZYLIDENE) p'-PROPYLANILINE IN
NEMATIC AND SOLID PHASES AS STUDIED BY DIELECTRIC RELAXATION SPECTROSCOPY
A. Baka, M. Massalska-Arodzb
and S. Urbanca Chair of Physics,
Technical University of Rzeszów, W. Pola 2, 35-959
Rzesz&owacute;, Poland
b Henryk Niewodniczański Institute of Nuclear
Physics
Radzikowskiego 152, 31-342 Kraków, Poland
c Institute of Physics,
Jagiellonian University, W. Reymonta 4, 30-059 Kraków, Poland
Received: August 20, 1999; revised version December 22, 1999
The complex dielectric permittivity
varepsilon*(nu,T)=varepsilon'
(nu,T)-i varepsilon''(nu,T) of n-p-(ethoxybenzylidene)
p'-propylaniline has been measured in the frequency range from 1 Hz to
13 MHz
and temperature range from 360 K to 180 K on heating and on cooling the
sample. Dielectric relaxations have been found in nematic and solid phases.
A detailed analysis of the observed processes has been performed and the
parameters describing molecular dynamics have been evaluated. The comparison
of results with those obtained for the other Schiff bases is
discussed.
PACS numbers: 64.70.Md, 77.22.Gm
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ANOMALOUS BEHAVIOR OF THE HALL EFFECT IN III-V HETEROSTRUCTURES
Z. Dziubaa, M. Górskaa,
J. Marczewskib, T. Przeslawskib
and K. Regińskiba Institute of Physics,
Polish Academy of Sciences
Al. Lotników 32/46,
02-668 Warsaw, Poland
b Institute of Electron Technology, Al. Lotników
32/46, 02-668 Warsaw, Poland
Received: August 31, 1999; revised version December 2, 1999
The Hall effect and magnetoresistance were measured in the InAs/GaAs
heterostructure at temperatures from 300 K down to 3 K, in a magnetic field
range from 0.01 to 1.5 T. The anomalous magnetic field dependence of the
Hall
coefficient in the InAs/GaAs heterostructure in magnetic fields below 0.1 T
was explained as due to an extraordinary Hall effect caused by skew
scattering on dislocations.
PACS numbers: 61.72.Lk, 72.80.Ey
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BEHAVIOUR OF THE OPTICAL BIREFRINGENCE
IN CONDITIONS OF THE
``VISCOUS''
INTERACTION
and Yu.I. PankivskyiLaboratory of Ecology, Department of Ecology,
Ukrainian State University of
Forestry
and Wood Technology, O. Kobylyanskoyi st. 1, Lviv, 79005, Ukraine
Received: September 23, 1999
The temperature dependences of optical birefringence delta(Delta n)
for the principal cuts of [N(CH3)4]2CuCl4
crystals are measured. On the
basis of the obtained experimental and theoretical data the anomalous
behavior of physical parameters in conditions of the ``viscous'' interaction
of the modulated structure with mobile defects in the incommensurate phase
is explained.
PACS numbers: 64.70.-p
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AB INITIO CALCULATIONS OF PHONON DISPERSION RELATIONS IN ALUMINIUM
P. Scharocha, K. Parlińskib
and A. Kiejnaca Institute of Physics, Wroclaw
University of Technology
Wyb. Wyspiańskiego 27, 50-370 Wroclaw, Poland
b Institute of Nuclear Physics,
Radzikowskiego 152, 31-342 Kraków, Poland
c Institute of Experimental
Physics, University of Wroclaw
Pl. M. Borna 9, 50-204 Wroclaw, Poland
Received: November 9, 1999
A direct method and ab initio force constants were used to calculate
phonon dispersion curves and phonon density in Al. The force constants were
determined from the Hellmann-Feynman forces induced by the displacement of
an atom in the 2×2×2 fcc crystallographic supercell. This size of
the supercell gives exact phonon frequencies at Gamma, X, L, W points of
the Brillouin zone. The calculated phonon dispersion curves are in good
agreement with the experimental data.
PACS numbers: 63.20.-e, 71.15.Nc
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INFLUENCE OF A ONE-ION ANISOTROPY
ON STABILIZATION
OF THE LONG-RANGE
MAGNETIC ORDER
IN TWO-DIMENSIONAL FERROMAGNET
Yu.N. Mitsaya, Yu.A. Fridmana,
D.V. Spirina and M.S. Kochmańskiba
V.I. Vernadsky Tavricheskii National University
333007, Yaltinskaya st.,
4, Simferopol, Ukraine
b Institute of Physics, University of Rzeszów,
Rejtana 16A, 35-310 Rzeszów, Poland
Received: October 19, 1999
In the paper the possibility of stabilization of the long-range
magnetic order in a two-dimensional ferromagnetic with one-ion easy-plane
anisotropy is explored. It is shown that at the presence of a small
anisotropy in a two-dimensional ferromagnetic the long-range magnetic order
is stabilized by magnetoelastic interaction. If one-ion anisotropy is
comparable or even exceeds the exchange interaction in the system there
exists a long-range non-vectorial quadrupolar tensorial magnetic
order.
PACS numbers: 75.10.-b, 75.30.Kz
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