Effect of incoherence of laser pulses on the signal characteristic in nonstationary active spectroscopy
Effect of incoherence of laser pulses on the signal characteristic in nonstationary active spectroscopy
S.Yu. Nikitin
We calculate the characteristics of the signal in nonstationary active spectroscopy with allowance for the finite duration and incoherence of laser pulses used in the excitation and probing of molecular vibrations of a substance. It is shown that in the short-pulse regime the form and duration of the observed pulsed response is determined only by the properties of the medium under investigation and is independent of the coherence of the laser pulses. The energy of the pulsed response decreases with increasing coherence.
Show AbstractNonlinear distortion of tubular beams in moving media
Nonlinear distortion of tubular beams in moving media
A.P. Sukhorukov, V.V. Timofeev, V.A. Trofimov
We analyze the nonlinear distortion of a two-dimensional light beam with a profiled amplitude distribution after passage through a layer of moving defocusing medium. It is shown that this beam suffers a nonlinear self-interaction which is smaller than that of a Gaussian beam. We obtain the condition for optimal defocusing.
Show AbstractSuppression of nonlinear damping of a sound wave in a medium which contains a resonant absorber with a finite line width
Suppression of nonlinear damping of a sound wave in a medium which contains a resonant absorber with a finite line width
V.G. Andreev, O.V. Rudenko, O.A. Sapozhnikov, V.A. Khokhlova
We obtain an evolution equation for waves in media with a quadratic nonlinearity and an arbitrary linear damping. This equation is used to analyze numerically the suppression of nonlinear damping of a harmonic sound wave in a medium which contains a resonant absorber at the frequency of the second harmonic. We find the region of values of the absorption coefficient and the region of the Q factors of the absorber in which this effect can be observed.
Show AbstractQuantitative study of the nonlinear transformation of sound pulses in liquid under thermooptical excitation
Quantitative study of the nonlinear transformation of sound pulses in liquid under thermooptical excitation
A.A. Karabutov, N.N. Omel'chuk, O.V. Rudenko, V.A. Chupryna
We make quantitative comparison of the theory of thermooptical generation for a planar problem with the experimental data on the thermooptical excitation of sound. The sound is excited by a pulsed $CO_2$ laser. The theoretical and experimental data are in good agreement.
Show AbstractPhase transitions in cholesteric liquid crystals with allowance for realistic optical activity of mesogenic molecules
Phase transitions in cholesteric liquid crystals with allowance for realistic optical activity of mesogenic molecules
G.A. Lyakhov, V.A. Makarov
It is shown that the optical activity of molecules which form the cholesteric liquid crystals must lead to a vectorial orientational order. It is suggested that the structure of this new type can be identified from the observation of "weak" optical activity.
Show AbstractEffect of oil pollution on the intensity of gas exchange between ocean and the atmosphere (on the example of the North Atlantic)
Effect of oil pollution on the intensity of gas exchange between ocean and the atmosphere (on the example of the North Atlantic)
V.V. Alekseev, P.A. Baranov, A.O. Kokorin, V.M. Sheremet'ev
We present the results of laboratory experiments which indicate that a hydrocarbon film has a considerable effect on the gas exchange between the water-air boundary under a weak collapse of waves and thermal convection. We analyze the data on the pollution of the North Atlantic by films of oil products. We estimate the rates of gas exchange between the ocean and atmosphere (on the example of the North Atlantic) caused by oil pollution.
Show AbstractSpherically symmetric model of elliptical galaxies in double systems. II. Comparison with observations
Spherically symmetric model of elliptical galaxies in double systems. II. Comparison with observations
V.V. Demin, M.V. Sazhin
We study a model of galaxies of the EE type with the average integral characteristics which were obtained earlier, and the density distribution which corresponds to the King's law. For this model, we study the region of possible motion of a material point in the framework of the problem of two stationary centers. The results obtained in this work are in favor of active gas exchange during the star-formation and supernovae explosions in the components of the pair which have an effect on the evolution of these double systems at the early stages of their existence.
Show AbstractChange of structure of the amorphous alloy $Co_{75}Fe_5B_{20}$ at the initial stage of recrystallization
Change of structure of the amorphous alloy $Co_{75}Fe_5B_{20}$ at the initial stage of recrystallization
P.N. Stetsenko, I. Pavlovskii, V.V. Surikov, S.D. Antipov, A.V. Garmashov
The effect of thermal processing of the structure of the amorphous alloy $Co_{75}Fe_5B_{20}$ is studied by measuring the NMR spectra, temperature dependences of the magnetization, and by X-ray structure analysis. The obtained data show that already in the initial amorphous state of the alloy $Co_{75}Fe_5B_{20}$ there exist regions with local environment similar to the crystal structure of $Co_3B$. It is assumed that the replacement of cobalt atoms by iron atoms assists the formation of these regions.
Show AbstractCharge accumulation in a semiconductor in a variable transverse field
Charge accumulation in a semiconductor in a variable transverse field
V.F. Kiselev, V.A. Matveev
We study the accumulation of positive charge when germanium surface is acted upon by transverse sinusoidal fields. It is shown that the accumulation effect takes place only in the presence of adsorbed water molecules on the surface, and is not observed in the atmosphere of other donor molecules. We develop a donor mechanism for the accumulation effect. We note that the dissociation constant of the adsorbed water molecules depends on the sign of the charge captured into the slow adsorption states.
Show AbstractM$\stackrel{..}{o}$ssbauer effect in paratellurite under pressure
M$\stackrel{..}{o}$ssbauer effect in paratellurite under pressure
A.A. Kornilova, E.V. Kapitanov, R.N. Kuz'min, A.A. Opalenko
We study the M$\stackrel{..}{o}$ssbauer effect in paratellurite monocrystals under hydrostatic pressure up to 30 kbar. We determine the pressure dependence of the probability of the M$\stackrel{..}{o}$ssbauer effect in monocrystals and polycrystals up to 50 kbar. We confirm the presence of a second-order phase transition at pressure 10 kbar above which we observe the disruption of monocrystals.
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