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  • Articles  (845,052)
  • Springer  (828,891)
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  • 1
    Electronic Resource
    Electronic Resource
    Assignment of the 5d6s-5d6p transitions in the PtIX ion: Comparison of two calculations of the 5d 2, 5d6s, and 5d6p configurations in the ion (2000)
    Springer
    Optics and spectroscopy 88 (2000), S. 11-16 
    Details
    ISSN: 1562-6911
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The spectrum of platinum is studied in the region from 250 to 1250 Å. The twenty-two 5d6s-5d6p spectral lines of the PtIX are assigned. All levels of the 5d6s configuration are found. The assignment of the previously known 5d6p levels is confirmed and their positions are refined. The 5d 2, 5d6s, and 5d6p configurations are theoretically described by the method of orthogonal operators. These calculations are compared with the data obtained by a conventional method using the Cowan program.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1134/1.626738
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  • 2
    Electronic Resource
    Electronic Resource
    Resonant multiphoton ionization of the 1s state of a hydrogen atom in a strong laser field (2000)
    Springer
    Optics and spectroscopy 88 (2000), S. 1-6 
    Details
    ISSN: 1562-6911
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The process of resonant multiphoton ionization of a hydrogen atom in the ground 1s state is studied by direct numerical integration of the nonstationary Schrödinger equation for a quantum system in an electromagnetic field. The dependence of photoionization probability on the radiation intensity is found to be nonmonotonic. It is established that the minima of ionization correspond to multiphoton resonances between the ground state and one of the excited (Rydberg) atomic states perturbed by the laser field. It is shown that ionization is suppressed due to rearrangement of Rydberg states in a strong electromagnetic field and is accompanied by efficient Raman Λ transitions, which connect a set of closely lying Rydberg states via the continuum.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1134/1.626736
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  • 3
    Electronic Resource
    Electronic Resource
    Diffraction of an ultrashort pulse by a slit (2000)
    Springer
    Optics and spectroscopy 88 (2000), S. 96-101 
    Details
    ISSN: 1562-6911
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract An analysis of a specific feature of the interaction of an ultrashort pulse with a slit is made. Analytical expressions for a monochromatic wave in the form of an ultrashort pulse diffracted by an infinite slit are obtained.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1134/1.626753
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  • 4
    Electronic Resource
    Electronic Resource
    Transformation of spatial modulation of a light field into amplitude modulation in the interaction of a superposition of transverse modes of a He-Ne laser with iodine-127 vapors (2000)
    Springer
    Optics and spectroscopy 88 (2000), S. 113-117 
    Details
    ISSN: 1562-6911
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The observation of “spatial-modulation” resonances of saturated absorption in the interaction of iodine-127 vapors with a superposition of frequency-nondegenerate TEM01 and TEM10 transverse modes of a linear laser is reported. The modulation of the total radiation power of the probing wave, recorded at twice the beating frequency of transverse modes of the laser, is interpreted to be the result of the transformation of modulation of the spatial distribution of the field into its amplitude modulation under the action of nonlinearly absorbing iodine vapors. Resonances of saturated absorption of the weak line R(127)11-5 of iodine-127 (633 nm) in an extracavity cell are observed by the method proposed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1134/1.626756
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  • 5
    Electronic Resource
    Electronic Resource
    Narrow saturated absorption resonances in the transmission band of an active interferometer (2000)
    Springer
    Optics and spectroscopy 88 (2000), S. 127-131 
    Details
    ISSN: 1562-6911
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The shape of the transmission band of an active interferometer, a resonator with amplification and absorption cells excited by an external signal, is studied. Upon tuning the external signal frequency, the narrow saturated absorption resonances can be observed in the transmission band of the interferometer. It is shown that, by varying the gain, the resonance absorption amplitude can be compensated for one order of smallness in pressure. The effect of amplitude and frequency noises of the external signal on the results obtained is studied.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1134/1.626759
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  • 6
    Electronic Resource
    Electronic Resource
    Electronic and spatial structures of the hydroxyl ion in LiF, NaF, and KF crystals (2000)
    Springer
    Optics and spectroscopy 88 (2000), S. 38-41 
    Details
    ISSN: 1562-6911
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The electronic and spatial structures of the impurity hydroxyl ion in LiF, NaF, and KF crystals are studied using a molecular cluster model by the Hartree-Fock-Roothaan method in the semiempirical INDO (intermediate neglect of differential overlap) approximation. The equilibrium geometry of the impurity ion is determined. The hydroxyl ion is oriented in all the three matrices along the 〈110〉-axis, which is caused by the formation of the selected chemical bond between the hydrogen ion and the nearest lattice fluorine ion located on the same axis. The optical absorption energies are calculated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1134/1.626743
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  • 7
    Electronic Resource
    Electronic Resource
    Nonlinear excitation of AgBr nanocrystals in the field of short light pulses (2000)
    Springer
    Optics and spectroscopy 88 (2000), S. 50-54 
    Details
    ISSN: 1562-6911
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Processes of the electron-hole pair generation and excited-state relaxation at earlier stages of the latent image formation in the AgBr nanocrystals are studied theoretically. The experimental dependence of the photographic blackening D in the field of the intense laser light on the light pulse energy I is analyzed in the range of pulse durations τi from 10−13 to 10−8 s. The values of I needed to obtain a fixed blackening D at τi∼10−10 s exceeded those at τi∼10−8 s by three orders of magnitude. However, as τi further decreased to hundreds of fs, these values decreased by two orders of magnitude. It is shown that experimental nonmonotonic dependences can be explained by saturation of the one-photon interband generation of electron-hole pairs accompanied by the development of the two-photon generation. For shortest pulses and, correspondingly, greatest light intensities, the pair generation rate varies more strongly than upon usual two-photon absorption, which is caused by the resonance optical Stark effect.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1134/1.626746
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  • 8
    Electronic Resource
    Electronic Resource
    Scattering of surface magnetic polaritons rom order-parameter fluctuations near second-order magnetic phase transitions (2000)
    Springer
    Optics and spectroscopy 88 (2000), S. 55-62 
    Details
    ISSN: 1562-6911
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A study is reported of the scattering of surface magnetic polaritons in the vicinity of second-order spin-reorientational phase transitions, which is caused by spatial fluctuations of the order parameter. A four-sublattice antiferromagnet α-Fe2O3 is used as an example to derive expressions for the vacuum-scattered radiation near exchange magnetic-vibration frequencies. The scattering of surface magnetic polaritons is shown to be resonantly enhanced in characteristic regions of their spectrum. Estimates made for α-Fe2O3 indicate a possibility of experimental observation of surface magnetic-polariton scattering from fluctuations of the refractive index near second-order spin-reorientational phase transitions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1134/1.626747
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  • 9
    Electronic Resource
    Electronic Resource
    On the stability of the phase problem (2000)
    Springer
    Astronomy letters 26 (2000), S. 49-60 
    Details
    ISSN: 1562-6873
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Phase retrieval of a signal given its intensity is considered as a problem of statistically estimating a set of unknown parameters, the Zernike coefficients. Specifically, the phase problem is presented in the context of classical wave optics in the Fresnel approximation. Investigating the stability in this case suggests first learning if the Zernike coefficients can be restored in principle. If this is indeed the case, it then suggests determining the accuracy of their estimation. The stability of a solution to the phase problem depends, as it does for the other inverse problems, on the spectrum of the Fisher information matrix. An explicit representation of the Fisher matrix is given, and its spectrum is calculated for in-focus and out-of-focus images of a pointlike source. Simulations show that the solutions in the latter case are generally stable, so the coefficients of the Zernike series can be determined with an acceptable accuracy. The principal components, the mutually independent combinations of aberrations that are a generalization of the coefficients of the well-known Karhunen-Loeve decomposition, are calculated. As an example of this approach, the maximum-likelihood method is used to determine the aberrations of the optical system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1134/1.20368
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  • 10
    Electronic Resource
    Electronic Resource
    Role of metastable atoms and molecules of helium in excitation transfer to hydrogen atoms (2000)
    Springer
    Optics and spectroscopy 88 (2000), S. 151-157 
    Details
    ISSN: 1562-6911
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The afterglow of a discharge in helium with a small admixture of hydrogen is studied spectroscopically (p=40 Torr, [e]≤1011 cm−3). The time-resolved measurements of intensities of the first four lines of the Balmer series are performed. The concentrations of metastable helium atoms and molecules are evaluated from the relative intensity of the absorption lines. The ratios of excitation transfer rates from atoms He(2 3 S 1) k 1(n) and molecules of helium He2(a 2sσ 3Σ u + ) k 2(n) to atomic hydrogen H*(n) are measured to be k 1(n=3)/k 2(n=3)=0.04±0.02 and k 1(n=4)/k 2(n=4)=0.01±0.02. The ratios of excitation rate constants k 2(n) corresponding to different states H(n) are measured to be k 1(n=4)/k 2(n=3)=0.023±0.01; k 1(n=5)/k 2(n=3)≤0.013; and k 1(n=6)/k 2(n=3)≤0.007.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1134/1.626770
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  • 11
    Electronic Resource
    Electronic Resource
    Localized optical structures in the scheme of a nonlinear layer with a feedback mirror (2000)
    Springer
    Optics and spectroscopy 88 (2000), S. 238-241 
    Details
    ISSN: 1562-6911
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract An analysis is made of the dynamics of the transverse structure of the field in the scheme of a layer of a medium with nonlinear amplitude-phase transmittance and a feedback mirror separated from it by a linear spacing. For the case of small field changes in a single passage, an approximate equation is derived, which is close in form to the equation used in the average-field approximation for nonlinear interferometers excited with external emission. For the nonlinearity of threshold type, an analytical form is presented for the field distribution corresponding to localized dissipative structures (dissitons).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1134/1.626785
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  • 12
    Electronic Resource
    Electronic Resource
    Elastooptic distortions in the second-harmonic generation in nonlinear crystals in the approximation of an elastic isotropic medium (2000)
    Springer
    Optics and spectroscopy 88 (2000), S. 266-271 
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    ISSN: 1562-6911
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The question of applicability of the approximation of an elastic isotropic medium to the description of elastooptic distortions in the second-harmonic generation in nonlinear crystals is analyzed. A method for a change to this approximation is proposed and the numerical calculation of elastooptic distortions in the secondharmonic generation is made for some crystals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1134/1.626790
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  • 13
    Electronic Resource
    Electronic Resource
    Weak-localization effect for light backscattered by surfaces with a complex structure (2000)
    Springer
    Optics and spectroscopy 88 (2000), S. 253-259 
    Details
    ISSN: 1562-6911
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Results of laboratory measurements of the weak-localization effect for light scattered by surfaces with different characteristics are presented. The measurements were made in a range of phase angles of 0.2°–3.5°. The aim of the measurements was to study the influence of the choice of surface material (metal, dielectric), the size of particles of the scattering surface, their packing density, the reflectivity of a sample, and the wavelength of incident radiation on the effect. For the measurements, both nonpolarized and linearly polarized light was used. Powders of dielectric materials were found to enhance the weak-localization effect with increasing particle size, but the effect weakened starting with a certain size of the order of wavelength. The pressing of powders of dielectric transparent materials enhanced the opposition effect. This was most pronounced for samples with small-sized particles. The phase dependence of brightness became wider and more linear with decreasing reflectivity of the surface. A qualitative difference in the behavior of the phase dependence for the ratio of cross-and copolarized components was observed. For metals and metal-like materials, the ratio increased with decreasing phase angle. Dielectrics were found to have an opposite dependence.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1134/1.626788
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  • 14
    Electronic Resource
    Electronic Resource
    Study of basic characteristics of radiation of flashlamps with microsecond discharge lengths (2000)
    Springer
    Optics and spectroscopy 88 (2000), S. 297-301 
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    ISSN: 1562-6911
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Spectral and temporal characteristics of xenon flashlamps are studied theoretically for the case of high-power nonstationary discharges of microsecond lengths. It is shown that several factors affect them simultaneously under these conditions: parameters of electric discharge pulse, thermal inertia of a heated gas, and the region of transparency of a lamp envelope.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1134/1.626764
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  • 15
    Electronic Resource
    Electronic Resource
    Special features of amplification of UV at the electronic transition of the CU+ ion in an NaCl crystal (2000)
    Springer
    Optics and spectroscopy 88 (2000), S. 310-311 
    Details
    ISSN: 1562-6911
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The spectral and luminescent properties of the Cu+ ion in an NaCl crystal are studied and the amplification is obtained at the 3d 10→3d 94P transition, which is under excitation by the fourth harmonic of an Nd:YAG laser (λ=266 nm). It is found that the short-lived absorption is related to an uncontrollable nickel impurity in the crystal.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1134/1.626767
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  • 16
    Electronic Resource
    Electronic Resource
    Semiempirical calculation of the fine-structure parameters for np 5 n′p configurations (2000)
    Springer
    Optics and spectroscopy 88 (2000), S. 321-326 
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    ISSN: 1562-6911
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The fine-structure parameters are calculated semiempirically in the intermediate coupling scheme for the np 5 n′p configurations of rare gas atoms and a number of ions. The calculation is based on the two-electron matrix of the energy operator, which takes into account, along with the electrostatic interaction, all magnetic interactions. Diagonalizing the energy matrix with the calculated values of the fine-structure parameters yields energy values exactly coinciding with the experimental data, as well as the coupling coefficients and the gyromagnetic ratios. The results obtained are compared with the available literature data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1134/1.626796
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  • 17
    Electronic Resource
    Electronic Resource
    Intramolecular vibrational modes of polychlorodibenzo-p-dioxines of the D 2h symmetry (2000)
    Springer
    Optics and spectroscopy 88 (2000), S. 339-345 
    Details
    ISSN: 1562-6911
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The infrared and Raman spectra of the octachlorodibenzo-p-dioxine molecule are measured and all normal vibrational modes of the molecule are calculated. Each vibrational mode was assigned to the vibrations of certain functional groups of atoms in the molecule, taking into account the local symmetry characteristics of the vibration mode. A correlation of vibrational modes by their shape was established in a series of molecules: dibenzo-p-dioxine, 2,3,7,8-tetrachlorodibenzo-p-dioxine, and OCDX. The influence of substituents on vibrational frequencies was also examined.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1134/1.626799
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  • 18
    Electronic Resource
    Electronic Resource
    On the propagation of electromagnetic pulses under the conditions of quasi-resonance (2000)
    Springer
    Optics and spectroscopy 88 (2000), S. 380-386 
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    ISSN: 1562-6911
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A theory of quasi-resonance for the model of atoms with an arbitrary number of levels is developed by the method of unitary transformation without recourse to Bloch’s equations. Corrections to the results known from the theory of adiabatic following, which refine these results and take into account dispersion of the nonlinear response of the resonant system, are obtained. The condition for quasi-resonance with a single atomic transition is shown to impose stringent limitations on the form of the nonlinear evolution equation for the electric field envelope of the pulse with dispersion of the nonlinear response taken into account, which prohibit the reduction of the equation indicated to familiar, fully integrable systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1134/1.626806
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  • 19
    Electronic Resource
    Electronic Resource
    Line phosphorescence spectrum of octachlorodibenzo-p-dioxine at 4.2 K (2000)
    Springer
    Optics and spectroscopy 88 (2000), S. 334-338 
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    ISSN: 1562-6911
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The line phosphorescence spectrum of octachlorodibenzo-p-dioxine (OCDX) is obtained and interpreted. The symmetry of the lowest triplet state of this molecule is established. The vibrational frequencies found from the vibronic phosphorescence spectrum at 4.2 k are assigned to the vibrational modes of certain symmetry related to individual functional atomic groups of the molecule. The relation between contributions from the spin-orbit (SO) and vibronic-spin-orbit (VSO) interactions to the phosphorescence rate constant k ph of the OCDX molecule is found from the vibronic line intensities. It is found that the increase in the number of Cl atoms in OCDX compared to that in tetrachlorobenzo-p-dioxine results in the increase in the relative contribution of the VSO interaction to k ph.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1134/1.626798
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  • 20
    Electronic Resource
    Electronic Resource
    Comparison of four methods for processing data on exponential decay (2000)
    Springer
    Optics and spectroscopy 88 (2000), S. 327-333 
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    ISSN: 1562-6911
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Using the decay of a single exponential function to a nonzero level as an example, the following numerical methods for determining lifetimes are considered: the least-squares method, the differentiation method, and two modifications of the method of moments. Domains of efficient application of one method or the other, depending on the form of the noise distribution, are determined on the basis of computer simulation in parameter space of the problem. For the Poisson noise distribution, a domain of parameters is found, where the error of determining the decay rate in the method of moments is smaller than in the least-squares method.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1134/1.626797
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  • 21
    Electronic Resource
    Electronic Resource
    Spectral variability of the X-ray pulsar Hercules X-1 (2000)
    Springer
    Astronomy letters 26 (2000), S. 691-698 
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    ISSN: 1562-6873
    Keywords: pulsars ; neutron stars ; X-ray sources ; scattering
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We present the results of our comparative timing and spectral analysis of the high and low (off) states in the X-ray pulsar Her X-1 based on data from the ART-P telescope onboard the Granat observatory. A statistically significant (several mCrab) persistent flux with a simple power-law spectrum was detected during the low state. The spectral slope changed from observation to observation by almost a factor of 2. Pulsations were detected only during the high state of the source, when its flux was a factor of ∼25 larger than the low-state flux. The spectral shape of Her X-1 in its high state was complex, with the parameters depending on pulse phase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1134/1.1323276
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  • 22
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    The temperature of nonspherical circumstellar dust grains (2000)
    Springer
    Astronomy letters 26 (2000), S. 679-690 
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    ISSN: 1562-6873
    Keywords: interstellar medium ; circumstellar shells
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The temperatures of prolate and oblate spheroidal dust grains in the envelopes of stars of various spectral types are calculated. Homogeneous particles with aspect ratios a/b≤10 composed of amorphous carbon, iron, dirty ice, various silicates, and other materials are considered. The temperatures of spherical and spheroidal particles were found to vary similarly with particle size, distance to the star, and stellar temperature. The temperature ratio T d(spheroid)/T d(sphere) depends most strongly on the grain chemical composition and shape. Spheroidal grains are generally colder than spherical particles of the same volume; only iron spheroids can be slightly hotter than iron spheres. At a/b≈2, the temperature differences do not exceed 10%. If a/b≥4, the temperatures can differ by 30–40%. For a fixed dust mass in the medium, the fluxes at wavelengths λ≥100 are higher if the grains are nonspherical, which gives overestimated dust masses from millimeter observations. The effect of grain shape should also be taken into account when modeling Galactic-dust emission properties, which are calculated when searching for fluctuations of the cosmic microwave background radiation in its Wien wing.
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    URL: http://dx.doi.org/10.1134/1.1316114
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  • 23
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    Energy release during disk accretion onto a rapidly rotating neutron star (2000)
    Springer
    Astronomy letters 26 (2000), S. 699-724 
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    ISSN: 1562-6873
    Keywords: neutron stars ; luminosity ; disk accretion ; X-ray bursters
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The energy release L s on the surface of a neutron star (NS) with a weak magnetic field and the energy release L d in the surrounding accretion disk depend on two independent parameters that determine its state (for example, mass M and cyclic rotation frequency f) and is proportional to the accretion rate. We derive simple approximation formulas illustrating the dependence of the efficiency of energy release in an extended disk and in a boundary layer near the NS surface on the frequency and sense of rotation for various NS equations of state. Such formulas are obtained for the quadrupole moment of a NS, for a gap between its surface and a marginally stable orbit, for the rotation frequency in an equatorial Keplerian orbit and in the marginally stable circular orbit, and for the rate of NS spinup via disk accretion. In the case of NS and disk counterrotation, the energy release during accretion can reach $$0.67\dot Mc^2 $$ . The sense of NS rotation is a factor that strongly affects the observed ratio of nuclear energy release during bursts to gravitational energy release between bursts in X-ray bursters. The possible existence of binary systems with NS and disk counterrotation in the Galaxy is discussed. Based on the static criterion for stability, we present a method of constructing the dependence of gravitational mass M on Kerr rotation parameter j and on total baryon mass (rest mass) m for a rigidly rotating neutron star. We show that all global NS characteristics can be expressed in terms of the function M(j, m) and its derivatives. We determine parameters of the equatorial circular orbit and the marginally stable orbit by using M(j, m) and an exact solution of the Einstein equations in a vacuum, which includes the following three parameters: gravitational mass M, angular momentum J, and quadrupole moment Ф2. Depending on Ф2, this solution can also be interpreted as a solution that describes the field of either two Kerr black holes or two Kerr disks.
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    URL: http://dx.doi.org/10.1134/1.1323277
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  • 24
    Electronic Resource
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    Simulation of shadings in systems of opaque particles (2000)
    Springer
    Optics and spectroscopy 88 (2000), S. 619-622 
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    ISSN: 1562-6911
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Results of computer simulation of the shading effect in systems of opaque spherical particles scattering light in accordance with the Lambert law are presented. Two types of systems are studied: a semi-infinite medium and statistically uniform clusters of a finite number of particles. The simulation makes it possible to obtain photometric characteristics of systems with an accuracy better than 1%. The phase dependence of the shading effect is shown to become steeper as the packing density of particles in clusters decreases and their number increases. For statistically uniform media, the following relation takes place: The lower the packing density, the more pronounced the shadow decrease in brightness with an increasing phase angle.
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    URL: http://dx.doi.org/10.1134/1.626848
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  • 25
    Electronic Resource
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    Results of the use of generalized coupling equations in the original Fresnel theory and original theory of spatial dispersion in a gyrotropic uniaxial crystal (2000)
    Springer
    Optics and spectroscopy 88 (2000), S. 630-633 
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    ISSN: 1562-6911
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The generalizations of the original Fresnel theory and original theory of natural gyrotropy as manifestations of the first-order natural dispersion in uniaxial crystals are considered. The generalizations are made for magnetic crystals, taking into account the magnetic gyrotropy. The region of application of the corresponding generalized theories is found to be restricted by a particular case of the wave normal s directed parallel to the optic axis C of a uniaxial crystal.
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    URL: http://dx.doi.org/10.1134/1.626850
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  • 26
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    Plasma resonance in granular gallium films deposited on rough NACl and KCl single-crystal surfaces (2000)
    Springer
    Optics and spectroscopy 88 (2000), S. 547-550 
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    ISSN: 1562-6911
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Granular gallium films deposited in high vacuum on the rough surfaces of NaCl and KCl single crystals maintained at 400°C consist of two layers, in which two resonance bands are excited simultaneously. In isolated grains of the upper layer, a band at the normal electron oscillation frequency ω0 is excited. As a result of supercooling, the grains are in the liquid state. The gallium plasma frequency calculated from the measured ω0 and dielectric constants of NaCl and KCl coincides with that obtained by other authors by metallooptic methods. In gallium deposited on room-temperature substrates, only one resonance band is excited, with the interband absorption band superposed on its low-frequency edge.
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    Comparison of semiempirical and ab initio absolute probabilities of rovibronic transitions for the I 1Π g − , J 1Δ g − →C 1Π u ± system of bands of the H2 molecule (2000)
    Springer
    Optics and spectroscopy 88 (2000), S. 676-685 
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    Topics: Physics
    Notes: Abstract The absolute values of probabilities of the I 1Π g − , v′, J′; J 1 Δ g − , v′, J′→C 1Π u ± , v″, J″ spontaneous transitions in the H2 molecule (for the vibrational and rotational quantum numbers v′=v″=0–3, J′=1–6, and J″=J′, J′ ±1) are calculated by using ab initio and semiempirical data on the dipole moments of the 3dπ 1Πg, 3dδ1Δg→2pπ1Πu electronic transitions. In both cases, the calculations are performed both in the adiabatic approximation and with an allowance for the nonadiabatic effect of electronic-rotational interaction. The coefficients of expansion of the wave functions of perturbed rovibronic states in the Born-Oppenheimer basis functions used in the calculations were obtained in the approximation of pure precession from experimental values of the terms. It was found that the values of transition probabilities based on the ab initio calculations systematically exceed the corresponding semiempirical data by a factor of 1.2–1.9 for the I 1Πg→C 1Π u ± transition and by a factor of 1.4–1.6 for the J 1Δ g − →C 1Π u ± transition. It was established that the difference between the ab initio and semiempirical values of electronic transition moments virtually has no effect on the dependence of the transition probabilities on the vibrational quantum numbers. The discrepancies between the results of adiabatic and nonadiabatic calculations are significant and reach two orders of magnitude, which is indicative of the important role of perturbations in the probabilities of the transitions considered.
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    Intramolecular vibrational energy transfer in mixtures of anthraquinone with foreign gases (2000)
    Springer
    Optics and spectroscopy 88 (2000), S. 705-712 
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    Topics: Physics
    Notes: Abstract Properties of collision transfer of vibrational energy in the vibrational quasi-continuum of mixed singlet-triplet levels of anthraquinone are studied by the method of time-resolved delayed fluorescence. The two-exponential fluorescence decay is analyzed in the kinetic approximation. It is shown that dependences of the intensities and decay rates of the fast and slow components on pressure can be used for estimating the rates of the establishment of the vibrational (V-V) and thermal (V-T) equilibrium. The efficiency β and the average energy 〈ΔE〉 transferred in collisions are estimated for these processes. It is found that the V-V process is characterized by high values of β, which, however, are lower in the quasi-continuum of mixed singlet-triplet states than the gas-kinetic values (β 〈 0.2). The transformation of the vibrational energy to the translational energy occurs with the low efficiency (10−2 〉 β 〉 10−5). The average energy 〈ΔE〉 transferred during a collision in the V-V process is comparable with the energy predicted by the statistical theory of ergodic transfer. The correlation between experimental and theoretical values improves when the time resolution of the experiment is sufficient for the separation of the V-V and V-T processes.
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    The formation of moving kinks under the effect of collimated tubular optical beams (2000)
    Springer
    Optics and spectroscopy 88 (2000), S. 725-728 
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    Topics: Physics
    Notes: Abstract The dynamics of switching waves in optically bistable systems on the basis of growing absorption is analyzed by quasi-optical description. A new scenario of kinks moving towards the optical beam under the action of a tubular optical beam is described. As opposed to an originally Gaussian beam focused on to the entrance face, a high intensity at the exit from the medium under the action of a collimated tubular beam is achieved due to the transformation of its profile. The structures formed are shown to be identical for both cases of action. The scenario of the development of moving switching waves found in this work is an alternative to that known in the literature earlier, which developed under the action of focused Gaussian beams and was analyzed with no regard for the variations of the phase of the optical beam.
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    Franck-Condon factor phase method for determining the potentials of bound states of piatomic molecules (2000)
    Springer
    Optics and spectroscopy 88 (2000), S. 852-856 
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    Notes: Abstract A new method for determining a fragment of the potential function of a bound state of a piatomic molecule from the phase of the matrix element of an electronic transition is proposed. As opposed to the method of WKB nodes [Opt. Spektrosk. 83, 906 (1997)], the new method (we call it the Franck-Condon factor phase method) is suitable for analyzing only those spectral regions free from interference structures. However, it is less demanding to the quality of experimental data and makes it possible to study situations where only a portion of the electronic band profile is accessible for analysis. Accuracy characteristics of the method are demonstrated using the analysis of the spectra of the transitions in Na2(23Σ g + (v=15, N=27; v=5, N=39)→3Σ u + ) as an example.
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    Oscillator strengths and transition energies of diamond (2000)
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    Optics and spectroscopy 88 (2000), S. 883-887 
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    Notes: Abstract The spectrum of the dielectric constant of three different samples of diamond in the 5–30-eV region is decomposed in thirteen elementary components. The main parameters of components are determined, and their nature is found on the basis of the band model.
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    Effect of the optical orientation of spin angular momenta of sodium atoms in the 32 S 1/2 state and metastable helium atoms in the 23 S 1 state on the Na-He gas-discharge plasma conduction (2000)
    Springer
    Optics and spectroscopy 88 (2000), S. 664-666 
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    Notes: Abstract The observation of the effect of mutual orientation of spin angular momenta of sodium atoms in the 32 S 1/2 state and helium atoms in the 23 S 1 state on the electrical conduction of a Na-He gas-discharge plasma is reported. In the experiments, a simultaneous optical orientation of atoms by the optical emission of sodium and helium lamps was carried out. The influence of the mutual orientation on the conduction was observed as a change in the high-frequency voltage across electrodes of a gas-discharge camera caused by the destruction of orientation of sodium atoms. The effect is explained by the dependence of Penning ionization in the interaction of sodium and helium atoms on the mutual orientation of spin angular momenta of partners.
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    Partial inversion in small molecules: New potentialities for the spectroscopic diagnostics of gases (2000)
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    Optics and spectroscopy 88 (2000), S. 696-704 
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    Notes: Abstract The formation of vibrational-rotational absorption spectra of small molecules in vibrationally non-equilibrium conditions, with the possibility of manifestation of partial population inversion of levels and negative absorption, is studied. Specific features of the partial inversion in linear and top molecules are analyzed. It is shown that water vapor is the best object among atmospheric gases for the realization of this effect. Formulas for the integrated line intensities and the absorption coefficient of two-and three-level nonequilibrium vibrational systems with a rotational structure are obtained. It is shown that the partial-inversion effect can be used to study weak vibrational-rotational transitions. Concrete calculations for the (000)-(010)-(020) bands of water molecules at different temperatures are made. The frequencies are determined for which negative absorption is the strongest.
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    Autocollimation reflection of light from the surface of corrugated waveguides with leaky modes (2000)
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    Optics and spectroscopy 88 (2000), S. 921-925 
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    Notes: Abstract The diffraction of light by a corrugated surface of a layered structure is studied. It is shown that the excitation of waveguide modes in a layered structure substantially changes the diffraction efficiency of a corrugated structure. In the autocollimation regime, the diffraction efficiency of a grating with a moderate depth may reach 100%. An increased Q factor of leaky modes was found to be the condition of efficient interaction of light with a grating.
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    Study of reverse absorption saturation in fullerene-containing polyimides (2000)
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    Optics and spectroscopy 88 (2000), S. 944-947 
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    Notes: Abstract The effect of reverse absorption saturation is studied in aromatic polyimides sensitized with fullerenes and a dye. The power density is estimated at which these systems can be most efficiently used to limit the laser radiation power. The data obtained are explained within the framework of the Förster model.
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    Excitation of a singly charged barium ion in electron-atom collisions (2000)
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    Optics and spectroscopy 89 (2000), S. 169-174 
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    Topics: Physics
    Notes: Abstract Results of the experimental study of excitation of transitions of singly charged barium atoms in collisions of low-energy monokinetic electrons with barium atoms are presented. Regularities of the behavior of cross sections for excitation in spectral series of BaII are found. The results are compared with other authors’ results.
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    Quantum-mechanical analysis of resonance Raman scattering spectra of the uracil molecule (2000)
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    Optics and spectroscopy 89 (2000), S. 205-210 
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    Notes: Abstract A direct quantum-mechanical calculation of the relative intensities of lines in the resonance Raman scattering (RRS) spectra of uracil is performed by a method developed earlier by the authors on the basis of the adiabatic model in the Herzberg-Teller approximation [1]. It is shown that the main regularities in the intensity distribution of spectra can be explained only by taking into account the vibronic mixing of electronic states and the contribution to the scattering tensor components from the excited electronic states adjacent to the resonance state. The calculated results are in satisfactory agreement with the results of experimental studies of the RRS spectra of uracil excited by laser radiation at 266, 240, 218, and 200 nm.
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    Determination of the distribution function of Stark dipole moments induced by a matrix in amorphous impurity systems (2000)
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    Optics and spectroscopy 89 (2000), S. 211-215 
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    Notes: Abstract The burning kinetics of closely spaced equidistant holes in impurity absorption spectra of glasses and polymers is theoretically studied in an alternating electric field (alternating in the magnitude, sign, and direction). The height of barriers between wells of the burnt multiwell spectral hole depends on the shape of the distribution of impurity molecules over the Stark dipole moments. Centrally symmetric impurity molecules are considered whose Stark moment is determined exclusively by the interaction with matrix molecules. Model calculations performed for different hypothetical distribution functions of Stark moments yield substantially different kinetics. Therefore, the method described allows one to verify experimentally various hypotheses about the nature of matrix-induced Stark moments.
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    Experimental measurement and calculation of the line intensities in vibronic spectra of jet-cooled anthracene (2000)
    Springer
    Optics and spectroscopy 89 (2000), S. 225-231 
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    Notes: Abstract The intensities of vibronic lines are experimentally measured in fluorescence and fluorescence excitation spectra of jet-cooled anthracene. An original method is developed for calculating geometrical parameters of benzene hydrocarbons in the ground and excited electronic states. Using these parameters, the intensities of vibronic lines in fluorescence and absorption spectra of anthracene are calculated in the Franck-Condon approximation taking into account the mixing of all the twelve normal coordinates of totally symmetric vibrational modes. After correction for the quantum yield of fluorescence, good agreement is obtained between the calculated line intensities in the absorption spectrum and the measured line intensities in the fluorescence excitation spectrum. Based on these data, a new assignment of the lines in the fluorescence excitation spectrum corresponding to totally symmetric modes 7 and 8 is suggested.
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    Absorption and fluorescent properties of pyrylium compounds: I. The nature of electronic transitions and structural rearrangement in the excited state (2000)
    Springer
    Optics and spectroscopy 89 (2000), S. 216-224 
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    Notes: Abstract The localization of molecular orbitals in 2,4,6-substituted derivatives of pyrylium is studied. The conformation of three asymmetrical molecules with oxyethyl substituents in positions 2 and 4 and different substituents in position 6 of the pyrylium ring is calculated by the AM1 method. The localization of the four upper occupied and two lower unoccupied MOs is determined, the fragment localization numbers are found, and the energies of five optical transitions, localization numbers, and the numbers of charge transfer between fragments are calculated. The conformation analysis of molecules in the S 0 and S 1 states is performed. Solid and liquid pyrylium solutions of different viscosity and polarity are experimentally investigated. The absorption spectra are recorded and absorption cross sections are measured, as well as fluorescence spectra and fluorescence anisotropy spectra. The following conclusions are made. In nonplanar molecules of pyrylium salts, four absorption transitions are localized at different parts of the molecule containing the pyrylium ring and one of the substituents. Upon excitation of molecules with complex substituents in position 6, the molecular fragment in position 2 turns around. This results in a flattening of the molecular fragment containing the pyrylium ring and substituents 2 and 6 on which the fluorescence transition is localized. The rearrangement involves the lowamplitude motion; it occurs almost without a loss of the excitation energy and only slightly affects the localization of molecular orbitals. As a result, two excited conformers are formed that possess close absorption and fluorescence properties. The radiative transitions in these conformers completely determine fluorescence of liquid solutions of any viscosity, including glycerol solutions. Strong solvatochromism is related to the nonplanar structure of stable pyrylium molecules, whereas the weak solvatochromism of liquid solutions is caused by localization of radiative transitions on a planar fragment of unstable fluorescing conformers.
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    Intermolecular interactions in the liquid crystal-fullerene C70 system (2000)
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    Optics and spectroscopy 89 (2000), S. 232-235 
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    Notes: Abstract The formation of complexes in the fullerene C70-toluene-liquid crystal system is investigated. The precision study of spectral manifestations of the intermolecular interaction in this system is performed for two low-frequency absorption bands of C70. These manifestations are found to be specific for each of the bands analyzed.
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    Isotropic acoustooptic Bragg diffraction in paratellurite by a slow shear wave (2000)
    Springer
    Optics and spectroscopy 88 (2000), S. 911-915 
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    Notes: Abstract An analysis is made of acoustooptic Bragg diffraction in a paratellurite crystal in the case of a slow shear acoustic wave. It is shown that the isotropic acoustooptic interaction in crystals has characteristic physical features, which distinguish it from the well-known anisotropic interaction. The isotropic interaction under study is shown to be a more complicated process than diffraction in optically isotropic media. A theoretical and experimental study of the dependences of Bragg angle of incidence on the ultrasound frequency was made. Expressions for the calculation of this dependence are presented, which give results that agree well with the experimental data. The dependences of the isotropic-diffraction efficiency on the acoustic power were studied. For the first time, it was found that the corresponding dependences for anisotropic and isotropic interactions are substantially different. It is shown that the isotropic interaction under study is weaker than the anisotropic interaction. However, the isotropic-diffraction efficiency has a noticeable value and can reach tens of a percent.
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    Excitation of quintet levels of MnII in electron collisions with manganese atoms (2000)
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    Optics and spectroscopy 89 (2000), S. 185-191 
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    Notes: Abstract Using extended crossing beams and optical spectroscopy, the excitation of transitions in the quintet system of MnII terms from the ground state of the manganese atom were studied. The results are compared with other authors’ data. For the levels z 5 P 1,2,3 0 , the branching ratios, the contribution of cascade transitions, and the cross sections for level excitation were determined.
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    Excitation of resonance lines of a Zn+ ion by electron impact (2000)
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    Optics and spectroscopy 89 (2000), S. 179-184 
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    Notes: Abstract Excitation of individual components of the resonance 4p 2 P 1 2,3/2/0 doublet of a Zn+ ion by electron impact is studied for the first time by the spectroscopic method in crossed beams. A distinct structure (above the ionization potential of an ion as well) found in the energy dependences of the effective excitation cross section is associated mainly with the decay to the resonance levels (direct or cascade) of autoionization states of zinc atoms and ions formed through the excitation of electrons from the subvalence 3d 10 shell. The results obtained are compared with data of other experiments and theoretical calculations by the method of strong coupling of five and fifteen states, as well as with the semiempirical calculation using the Van Regemorter formula.
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    Optical self-induced transparency in anisotropic dielectric crystals (2000)
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    Optics and spectroscopy 89 (2000), S. 287-289 
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    Notes: Abstract Optical self-induced transparency for extraordinary waves in anisotropic crystals is theoretically studied. Crystals in which dipole moments of impurity optically active atoms are arbitrarily oriented relative to the optic axis are analyzed in detail. Explicit analytic expressions for the parameters of nonlinear extraordinary wave are presented, which yield known results in limiting cases.
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    Mathematical modeling of random coupling between polarization modes in single-mode optical fibers: VI. Evolution in the degree of polarization of nonmonochromatic radiation traveling in a twisted optical waveguide (2000)
    Springer
    Optics and spectroscopy 89 (2000), S. 273-281 
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    Notes: Abstract An analysis is made of the evolution of polarization of nonmonochromatic radiation travelling through single-mode optical fibers in the presence of random coupling between orthogonally polarized modes, which is caused by the random twist of axes of natural linear birefringence of an SMF, and in the presence of a regular axis twist. It is shown that the depolarization length of nonmonochromatic radiation in an SMF increases with increasing regular SMF twist, regardless of the presence of a random axis twist. Using the Monte Carlo method, the dependences of the mathematical expectation and the mean-square deviation of the degree of polarization of nonmonochromatic radiation on the fiber length for SMFs with different linear birefringences and regular axis twists are calculated. It is shown that the fiber length on which the degree of polarization of nonmonochromatic radiation reaches its limiting value increases and the limiting value itself decreases with an increasing regular twist. It is also shown that an induced SMF twist is able to improve parameters of a fiber interferometer, in particular, to decrease random phase changes and intensity fadings of the interference signal, which are caused by random coupling between polarization modes.
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    Study of the possibility to measure the root-mean-square roughness of a shaded rough surface (2000)
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    Optics and spectroscopy 89 (2000), S. 397-401 
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    Notes: Abstract The estimate of the root-mean-square roughness of a rough surface σ1 is studied experimentally as a function of the angle of incidence. A surface with σ=1.3 μm is illuminated by laser radiation with a wavelength of 0.633 μm. The angle of incidence of radiation on the surface under study is varied from 85° to 87.5°. σ1 is estimated under the assumption that the regime of a slightly rough surface is fulfilled for the surface studied. Theoretical estimates of σ1 are calculated in the Kirchhoff approximation with rough surface shadowing taken into account. The greatest relative difference between experimental and theoretical estimates of σ 1 does not exceed 0.07. The effect of rough surface shadowing on the estimate of σ is analyzed, and the possibility for exact measurement of σ1 of a shaded rough surface is demonstrated in the case of a priori knowledge of the angle of incidence, for which this measurement is possible. A method that makes it possible to determine the angle of incidence, for which a good agreement between the measured value and the true value of σ of a shaded rough surface is possible, is proposed.
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    Diagnostics of a strong magnetic field using spectropolarimetry of the decaying emission (2000)
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    Optics and spectroscopy 89 (2000), S. 348-351 
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    Notes: Abstract A method for diagnostics of a magnetic field is suggested. The method is based on spectropolarimetry of the decaying emission of an ensemble of particles whose angular momenta were ordered by pulsed axially symmetric perturbation.
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    Optical transitions in molecules stimulated by inelastic collisions with fast particles (2000)
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    Optics and spectroscopy 89 (2000), S. 356-359 
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    Notes: Abstract The spectrum of absorption of light by a molecule colliding with a fast proton is considered. It is shown that the envelope of spectrum is an oscillating function with two maxima shifted toward lower and higher frequencies compared to the frequency of a Franck-Condon transition.
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    A Mechanism of the influence of Gd(III) and other Ln(III) ions on sensitized luminescence of Eu(III) and Tb(III) ions in aqueous and ethanol solutions: The role of hydroxyl bridges (2000)
    Springer
    Optics and spectroscopy 89 (2000), S. 360-368 
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    Notes: Abstract We studied sensitization of Eu(III) and Tb(III) ions by molecules of 1,10-phenanthroline and 2,2-bipyridil in D2O and d 6-ethanol and the influence of Nd(III), Pr(III), Sm(III), Gd(III), and Ho(III) ions on the luminescence intensity I lum and lifetime τlum of Eu(III) and Tb(III) in solutions. The stability constants of complexes of Eu(III) and Gd(III) with 2,2′-bipyridil are measured by spectrophotometric and luminescence methods. It is shown that luminescence of Eu(III) is quenched by Gd(III) ions at the ion concentration equal to 10−2–10−1 M, which is caused by competing between these ions for a sensitizer. At the concentration of Ln(III) ions equal to 10−6−10−3 M, the sensitized luminescence of Eu(III) and Tb(III) was quenched and τlum decreased in the presence of Nd(III) ions, whereas in the presence of Gd(III) the luminescence intensity increased. It is proved that a bridge that connects the two ions upon energy transfer is formed by hydroxyl groups. The intensity of luminescence of Eu(III) and Tb(III) in aqueous solutions and its lifetime decreased in the presence of hydroxyl groups, while upon addition of Gd(III) to these solutions these quantities were restored. We also found that the addition of Gd(III) to deoxygenated ethanol solutions of 2,2′-bipyridil and Eu(III) slows down photochemical and thermal reactions between bipyridil and Eu(III), resulting in the increase in the luminescence intensity of Eu(III).
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    Spectroscopic studies of sorbing fibers using combined elements with multiple attenuated total internal reflection (2000)
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    Optics and spectroscopy 89 (2000), S. 413-417 
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    ISSN: 1562-6911
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Spectroscopic studies of sorbing devices on the basis of silica capillaries coated by sorbing polymer films are carried out by methods of spectroscopy of multiple attenuated total internal reflection with the use of combined elements of internal reflection. A technique for inspecting and improving the technological process of manufacture of sorbing devices for solid-phase microextraction and subsequent chromatographic analysis of organic compounds is developed.
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    URL: http://dx.doi.org/10.1134/1.1310710
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    Weakly nonparaxial spatial solitons in a medium with Kerr nonlinearity (2000)
    Springer
    Optics and spectroscopy 89 (2000), S. 422-428 
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    ISSN: 1562-6911
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A version of perturbation theory is developed that intends to determine the field distribution of spatial solitons with a 2D transverse profile in a Kerr medium in the case of small deviations from paraxial conditions. An approximate master equation for transverse components of the electric field in the case of wide solitons is derived. By solving this equation starting from the unperturbed soliton, i.e., Townes mode with linear polarization of radiation, a solution with an axially symmetric field distribution is found. Dependences of the main soliton characteristics on the degree of paraxiality are determined.
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    Optical reflection from dielectric layers containing metal particles formed by ion implantation (2000)
    Springer
    Optics and spectroscopy 89 (2000), S. 408-412 
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    ISSN: 1562-6911
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Dielectric layers with silver nanoparticles, which are synthesized in a soda-silicate glass by implantation of 60-keV ions with a dose of 7.0×1016 Ag+/cm2 at an ion current density of 10 μmA/cm2, are analyzed. The depth of silver distribution was measured by Rutherford backscattering. Data on optical characteristics of composite layers were obtained from the transmission spectra and from the reflection, which were measured both from the side of an implanted glass surface and from the unimplanted side. To calculate reflection spectra, a multilayer plane-parallel film structure was considered, which was modeled on the basis of the matrix method using complex Fresnel coefficients. Dielectric functions of separate layers were determined using the Maxwell-Garnet theory of an effective medium. A qualitative agreement between the experimental and the model optical spectra was obtained taking into account a nonuniform depth distribution of metal nanoparticles in a composite material.
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    URL: http://dx.doi.org/10.1134/1.1310709
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    Formation of the holographic image of a diffuse object in second-harmonic radiation generated by a nonlinear medium (2000)
    Springer
    Optics and spectroscopy 89 (2000), S. 476-483 
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    ISSN: 1562-6911
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Results of experiments on recording three-dimensional holographic images of extended diffuse objects using an SHG hologram generating the second harmonic are presented. In this case, the object image is formed by the second-harmonic radiation whose wavelength is smaller than the wavelength of object and reference waves recorded on a hologram by a factor of two. Elements of the theory of an SHG hologram are considered. A holographic image of a transparency object illuminated with diffuse light is obtained. It is shown that the resolving power of this image is close to the limit determined by diffraction effects. An experiment on defocusing the reconstructed image showed that it was localized in one spatial plane and, therefore, was three-dimensional.
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    URL: http://dx.doi.org/10.1134/1.1310719
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    Determination of optical constants of latex in concentrated suspensions (2000)
    Springer
    Optics and spectroscopy 89 (2000), S. 756-760 
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    ISSN: 1562-6911
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The possibility of taking into account concentration effects in the determination of optical constants of latex in the visible and near IR regions of the spectrum is demonstrated, and the limits of applicability of the methods proposed for this purpose are determined. The limiting concentration of particles in suspensions for which these effects should be taken into account depend on the particle size. Using latex as an example, ways of increasing the accuracy of reconstruction of optical constants of weakly absorbing particles of micron and submicron size are shown. Similar concentration effects can take place in the study of blood substituents, proteins, and other weakly absorbing particles in weakly absorbing media.
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    URL: http://dx.doi.org/10.1134/1.1328134
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    Observations of the gamma-ray flux from the galaxy Mk 501 (2000)
    Springer
    Astronomy letters 26 (2000), S. 199-203 
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    ISSN: 1562-6873
    Keywords: active galactic nuclei ; gamma-ray observations ; quasars and radio galaxies
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We present two-year-long observations of the flux of very-high-energy (∼1012 eV) gamma rays from the active galactic nucleus Mk 501 performed with a Cherenkov detector at the Crimean Astrophysical Observatory. A gamma-ray flux from the object was shown to exist at confidence levels of 11 and 7 standard deviations for 1997 and 1998, respectively. The flux varied over a wide range. The mean flux at energies 〉1012 eV, as inferred from the 1997 and 1998 data, is (5.0±0.6)×10−11 and (3.7±0.6)×10−11 cm−2 s−1, respectively. The errors are the sum of statistical observational and modeling errors. The mean power released in the form of gamma rays is ∼2×1043 erg s−1 sr−1.
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    Mesostructure of the solar granulation (2000)
    Springer
    Astronomy letters 26 (2000), S. 192-197 
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    ISSN: 1562-6873
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Quasi-periodic variations in the thermodynamic and hydrodynamic fine-structure properties of the granulation field along the photospheric surface are estimated quantitatively. The darkest vast intergranular lanes, called the intergranular knots, are the most important indicator of their physical properties. The formulated new definitions of “granule” and “intergranular lane” require a revision of the previous results. The definition of mesogranulation is given, and the method of its detection in the granulation field is described. The following important quantitative results, which established the extent and nature of the physical relationship between the granulation and mesogranulation fields, have been obtained for the first time: (1) the intensity amplitude of granules in mesogranules (ΔI(gr)/I 0)msgr = +10.3% is a factor of 1.4 larger than that of granules in intermesogranular regions [(ΔI(gr)/I 0)imsgr = +7.3%], whereas the intensity amplitude of intergranular lanes in mesogranules [(ΔI(igr)/I 0)msgr = −6.0%] is a factor of 1.4 smaller than that of intergranular lanes in intermesogranular regions [(ΔI(igr)/I 0)imsgr = −8.4%]; (2) the mean intensities of photospheric granules and intergranular lanes are (ΔI(gr)/I 0)phot = +9.2% and (ΔI(igr)/I 0)phot = −7.5%, respectively; (3) granules cover 59% of the area of mesogranules, 45% of the area of the photosphere, and 31 % of the area of intermesogranular regions, while intergranular lanes cover 41, 55, and 69% of these areas, respectively; (4) intergranular knots and bright granules virtually never formed and do not exist in mesogranules and intermesogranular regions, respectively; (5) the amplitudes of intensity fluctuations in mesogranules and intermesogranular regions, as well as the areas occupied by them (49.4 and 50.6%, respectively), essentially level off, ΔI(msgr)/I 0 = +3.6% and ΔI(imsgr)/I 0 = −3.5%, respectively.
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    Observations of extragalactic radio sources at 36 GHz (2000)
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    Astronomy letters 26 (2000), S. 204-207 
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    ISSN: 1562-6873
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The observations of 34 extragalactic radio sources with the 22-m Crimean Astrophysical Observatory radio telescope at 36 GHz in 1985–1994 are presented. Intensity variations were detected in 27 objects, which may result from the appearance of new components in their cores.
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    Photometric deprojection of edge-on galaxies (2000)
    Springer
    Astronomy letters 26 (2000), S. 219-224 
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    ISSN: 1562-6873
    Keywords: galaxies ; structure and photometry of galaxies
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Photometric deprojection is used to determine the stellar-disk and bulge parameters for several edge-on galaxies from the FGC catalog. The assumption that the galaxies of our sample belonging to the fourth (i.e., lowest) surface-brightness class in the FGC are edge-on, low-surface-brightness (LSB) galaxies is considered.
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    On the internal structure of relativistic jets (2000)
    Springer
    Astronomy letters 26 (2000), S. 208-218 
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    ISSN: 1562-6873
    Keywords: accretion ; jet theory and stellar wind
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A magnetohydrodynamic model is constructed for a cylindrical jet embedded in an external uniform magnetic field. It is shown that, as in the force-free case, the total electric current within the jet can be zero. The particle energetics and the magnetic-field structure are determined in a self-consistent way; all jet parameters depend markedly on the physical conditions in the external medium. In particular, we show that a region with subsonic flow can exist in the central jet regions. In real relativistic jets, most of the energy is transferred by the electromagnetic field only at a sufficiently large magnetization parameter σ〉106. We also show that, in general, the well-known solution with a central core B Z =B 0/(1+ϖ2/ϖ c 2 ) cannot be realized in the presence of an external medium.
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    Dynamical stability of triple stars (2000)
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    Astronomy letters 26 (2000), S. 250-260 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The dynamical stability of 38 observed hierarchical triple stars with known orbital elements of the internal and external binary subsystems and component masses is considered. Four different criteria of dynamical stability are used. The observed stability parameters and their critical values are calculated by taking into account errors in the orbital elements and component masses. Most triple systems are stable. According to some criteria, several triple stars (ADS 440, ξ Tau, λ Tau, ADS 3358, VV Ori, ADS 10157, HZ Her, Gliese 795, ADS 15971, and ADS 16138) may be dynamically unstable. This result is probably associated with unreliability of the empirical stability criteria and/or with errors in the observed quantities.
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    A photometric and spectroscopic study of the Herbig Ae/Be star XY Per (2000)
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    Astronomy letters 26 (2000), S. 233-243 
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    ISSN: 1562-6873
    Keywords: stars—variable and peculiar
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The UBVR photometry of XY Per in 1985–1998 is presented. At this epoch, XY Per exhibited variability with an amplitude of ≈1m in V. The photometric variability of XY Per can be divided into three components: (1) smooth year-to-year variations in mean brightness; (2) quasi-periodic variations with a characteristic time scale of 20–40 days and an amplitude of $$0\mathop .\limits^m 3$$ ; and (3) Algol-like minima with a duration of 15–20 days and an amplitude of $$0\mathop .\limits^m $$ . The CLEAN algorithm is used to refine the quasi-period of light variations in the interval 1988–1995, $$P = 22\mathop .\limits^d 7252$$ . The observed variability is assumed to be produced by two mechanisms: circumstellar absorption and nonstationary accretion. An ultraviolet excess was observed in the stellar radiation during the local minimum of 1991, which was associated with an eclipse of the star by a circumstellar formation. The probable reason why it emerged is that part of the eclipsing circumstellar formation fell into the accretion zone. A high-esolution spectrum in the wavelength range 3600–6700 Å contains both photospheric lines and circumstellar shell lines. The shell line profiles suggest mass accretion onto the star at a velocity of 90–140 km s−1. Of the Balmer lines, only Hα is in emission. Its equivalent width is E(E λ). The strongest Fe II lines, as well as Mg II 4481.33 Å and He I 5875.65 Å, have an emission component at the line center. The presence of emission components in lines with different excitation potentials suggests the presence of a hot gas shell around the star, which is heated very nonuniformly.
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    Analysis of HST ultraviolet spectra for T Tauri stars: RU Lup (2000)
    Springer
    Astronomy letters 26 (2000), S. 225-232 
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    ISSN: 1562-6873
    Keywords: stars—variable and peculiar ; T Tau stars
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The ultraviolet spectra of the star RU Lup obtained with the Hubble Space Telescope are analyzed. Emission lines are identified. The presence of absorption components with a nearly zero residual intensity in the Mg II resonance doublet lines is indicative of mass outflow with a velocity V ∞≃300 km s−1. These lines also exhibit a broad (≃1400 km s−1 at the base) component originating in the star itself. The profiles of the (optically thin) Si II] and Si III]1892 Å lines for the first time unequivocally prove that these lines originate in an accretion shock wave rather than in the chromosphere, with the gas infall velocity being V 0≃400 km s−1. The intensity ratio of the C IV 1550 Å and Si IV 1400 Å resonance doublet components was found to be close to unity, suggesting a high accreted-gas density, logN 0〉12.5. Molecular H2 Lyman lines formed in the stellar wind were detected. The H I Lα luminosity of RU Lup was found from their intensities to exceed 10% of L bol. Radiation pressure in the Lα line on atomic hydrogen may play a significant role in the initial acceleration of stellar-wind matter, but the effect of Lα emission on the dynamics of molecular gas is negligible.
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    Continuum spectrum of the star Θ1 Ori C (2000)
    Springer
    Astronomy letters 26 (2000), S. 244-249 
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    ISSN: 1562-6873
    Keywords: stars—structure and evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Published photoelectric measurements over a wide wavelength range (0.36–18 µm) are used to study the continuum spectrum of the star Θ1 Ori C. The model that assumes the following three radiation sources is consistent with observations: (1) a zero-age main-sequence O7 star (object 1) of mass M 1=20M ⊙, radius R 1=7.4R ⊙, effective temperature T 2=37 000 K, and absolute bolometric magnitude $$M\mathop {bol}\limits^1 = - 7\mathop .\limits^m 7$$ ; (2) object 2 with M 2=15M ⊙, R 2=16.2R ⊙, T 2=4000 K, and $$M\mathop {bol}\limits^2 = - 5\mathop .\limits^m 1$$ ; and (3) object 3 with R 310 700 R ⊙, T 3=190 K, and $$M\mathop {bol}\limits^3 = - 0\mathop .\limits^m 6$$ . The visual absorption toward the system is $$A_V = 0\mathop .\limits^m 95$$ and obeys a normal law. The nature of objects 2 and 3 has not been elucidated. It can only be assumed that object 2 is a companion of the primary star, its spectral type is K7, and it is in the stage of gravitational contraction. Object 3 can be a cocoon star and a member of the system, but can also be a dust envelope surrounding the system as a whole.
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    Early afterglows of short gamma-ray bursts (2000)
    Springer
    Astronomy letters 26 (2000), S. 269-276 
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    ISSN: 1562-6873
    Keywords: gamma-ray bursts
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract In the relativistic fireball model, the afterglow of a gamma-ray burst (GRB) is produced by synchrotron radiation of the electrons accelerated in the external shock that emerges as the relativistic flow moves. According to this model, the afterglow peaks on a time scale of ∼10 s when observed in the soft gamma-ray band. The peak flux can be high enough to be detected by modern all-sky monitors. We investigate the emission from short (ΔT〈1 s) GRBs on a time scale t≈10 s using BATSE/CGRO data. A significant flux is recorded for ∼20% of the events. In most cases, the observed persistent emission can be explained in terms of the model as an early burst afterglow. No early afterglows of most short GRBs are observed. The model parameters for these bursts are constrained.
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    Internal rotation of the Sun as inferred from GONG observations (2000)
    Springer
    Astronomy letters 26 (2000), S. 261-267 
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    ISSN: 1562-6873
    Keywords: solar oscillations ; solar differential rotation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Helioseismology is a direct and most informative method of studying the structure and dynamics of the Sun. Determining the internal differential rotation of the Sun requires that the frequencies of its eigentones be estimated with a high accuracy, which is possible only on the basis of continuous long-term observations. The longest quasi-continuous series of data have been obtained by the Global Oscillation Network Group (GONG). The parameters of each individual mode of solar acoustic oscillations with low spherical degrees l=0, 1, 2, 3, 4, 5, 6 are determined by using 1260-day-long series of GONG observations. The mean frequency splitting by rotation for the modes of each radial order n is calculated by using all possible combinations between the eigenfrequencies in multiplets. As a result, it has become possible to statistically estimate the splitting and its measurement errors for the modes of each radial order. The mean splitting for each given degree l=1–6 is presented under the assumption of its independence of oscillation frequency, which holds for the achieved accuracy. The frequencies and splittings for the modes with low spherical degrees l, together with the MDI group results for higher degrees l, are used to invert the radial profile of solar angular velocity. Using the SOLA method to solve the inverse problem of restoring the rotation profile has yielded solutions sensitive to the deepest stellar interiors. Our results indicate that the solar core rotates faster than the surface, and there may be a local minimum in angular velocity at its boundary.
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    The polar stellar ring and dark halo of NGC 5907 (2000)
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    Astronomy letters 26 (2000), S. 277-284 
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    ISSN: 1562-6873
    Keywords: galaxies ; groups and clusters of galaxies ; intergalactic gas
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Numerical simulations of the disruption of a dwarf companion moving in the polar plane of a massive galaxy are presented. The constructed model is compared with observational data on the recently discovered low-surface-brightness stellar ring around the galaxy NGC 5907. Constraints on the ring lifetime (≤ 1.5 Gyr after the first approach of the galaxies), on the structure of the companion—the ring precursor, and on the mass of the dark halo of the main galaxy in whose gravitational field the companion moves are provided. The dark-halo mass within 50 kpc of the NGC 5907 center cannot exceed 3 or 4 “visible” masses.
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    Vorontsov-Velyaminov rows: Straight segments in the spiral arms of galaxies (2000)
    Springer
    Astronomy letters 26 (2000), S. 285-296 
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    ISSN: 1562-6873
    Keywords: galaxies ; spiral pattern ; Vorontsov-Velyaminov rows
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The phenomenon of rows—straight features in the spiral patterns of galaxies, which was discovered by Vorontsov-Velyaminov, is investigated. The rows are not artifacts; in several cases, they outline regular spiral arms almost over their entire lengths. The galaxies M 101, M 51, and a number of more distant spirals are used as examples to demonstrate major geometrical and physical properties of these structures. It is shown that the row lengths increase nearly linearly with distance from the disk center, and that the angle between adjacent rows is almost always close to 2π/3. The galaxies with rows generally belong to moderate-luminosity Sbc-Sc systems with low rotational velocities, regular spiral patterns (Grand Design), and an H I content normal for these types of galaxies. Two types of rows are shown to exist, which differ in thickness and appear to be evolutionarily related. The formation mechanism of the rows should probably be sought in the peculiar behavior of the gas-compression wave in spiral density waves.
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    Optical control of the edge of the band gap of semiconductor layered Fabry-Perot type structures (2000)
    Springer
    Optics and spectroscopy 89 (2000), S. 418-421 
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    ISSN: 1562-6911
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A mechanism of controlling light is studied, which is based on the change of refractive indices of narrow-gap layers in a semiconductor layered periodic Fabry-Perot type structure (superlattice) caused by the contribution of nonequilibrium charge carriers produced by controlling radiation. By choosing the wavelength of controlling light near the edge of intrinsic absorption of narrow-gap layers and by choosing the wavelength of controlled light near the edge of the band gap of a structure, one can obtain for 1.5-μm controlled radiation the modulation depth above 90%, with controlling radiation intensity of ∼6 kW/cm2.
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    Non-LTE effects for Na I lines in X-ray illuminated stellar atmospheres (2000)
    Springer
    Astronomy letters 26 (2000), S. 309-318 
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    ISSN: 1562-6873
    Keywords: stars—structure and evolution ; binary stars ; stellar atmospheres
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The formation of Na I lines in X-ray illuminated atmospheres is investigated by abandoning the assumption of local thermodynamic equilibrium (LTE). Calculations are performed on the basis of a 21-level Na I model atom for the LTE model atmospheres of irradiated F-G stars obtained with allowance for a reflection effect in the first approximation. The state of extreme “overrecombination” is shown to exist for the populations of all Na I levels in the case of external illumination. Absorption features in the profiles of “cool” and “normal” Na I lines have been found to be enhanced compared to the LTE approximation. Effects of the angle of incidence and intensity of the external radiation on the formation of level populations and line profiles when abandoning LTE are analyzed. The existence of overrecombination for Na I is explained by the small X-ray heating function and the large optical cooling function. Na I level populations are shown to depend weakly on the presence of “overionization” for Na II in the atmospheres of irradiated stars.
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    Linear polarization of precataclysmic variables (2000)
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    Astronomy letters 26 (2000), S. 319-321 
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    ISSN: 1562-6873
    Keywords: stars—variable and peculiar
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The optical linear polarization of three precataclysmic variables was measured in B and R. A noticeable polarization was detected only in BD +50°2869. In the other two cases, the polarization is probably interstellar in origin.
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    Prominence height and vertical gradient in magnetic field (2000)
    Springer
    Astronomy letters 26 (2000), S. 322-327 
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    ISSN: 1562-6873
    Keywords: plasma astrophysics ; hydrodynamics and shock waves ; Sun
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The existence of a critical height for quiescent prominences and its relationship to parameters of the magnetic field of photospheric sources are discussed. In the inverse-polarity model, stable equilibrium of a filament with a current is possible only in the region where the external field decreases with height no faster than ∼1/h. Calculations of the potential magnetic field above the polarity-inversion line are compared with the observed prominence height. The prominence height is shown to actually depend on the vertical field gradient and does not exceed the level at which the exponent of field decrease is equal to unity.
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    Minicomets in the Solar system and in the Earth’s atmosphere and related phenomena (2000)
    Springer
    Astronomy letters 26 (2000), S. 328-330 
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    ISSN: 1562-6873
    Keywords: minicomets ; bolides ; upper atmosphere
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We consider the history of discovery and justify the existence in the Solar system of a new class of bodies—minicomets, i.e., bodies of cometary nature and composition but of low mass. Two classes of minicomets are distinguished: icy ones similar to the Tunguska meteorite, and snow ones, which break up at high altitudes.
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    Asymmetric periodic solutions of the averaged Hill problem with allowance for a planet’s oblateness (2000)
    Springer
    Astronomy letters 26 (2000), S. 331-337 
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    ISSN: 1562-6873
    Keywords: averaged Hill problem ; periodic solutions ; torbital evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We consider asymmetric periodic solutions of the double-averaged Hill problem by taking into account oblateness of the central planet. They are generated by steady-state solutions, which are stable in the linear approximation and correspond to satellite orbits orthogonal to the line of intersection of the planet’s equatorial plane with the orbital plane of a disturbing point. For two model systems [(Sun+Moon)-Earth-satellite] and [Sun-Uranus-satellite], these periodic solutions are numerically continued from a small vicinity of the equilibrium position. The results are illustrated by projecting the solutions onto the (pericenter argument-eccentricity) and (longitude-inclination) planes.
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    A self-similar solution for spherically symmetric gravitational collapse (2000)
    Springer
    Astronomy letters 26 (2000), S. 344-355 
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    ISSN: 1562-6873
    Keywords: plasma astrophysics, hydrodynamics and shock waves ; supernovae and supernova remnants
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A model of gas-dynamical flow during gravitational collapse is analyzed mathematically by assuming its spherical symmetry and self-similarity. A shock wave diverging from the center emerges in this model. The physical requirements imposed on the post-shock flow at the center for the specified parameters at infinity unambiguously determine the shock front and the flow behind it.
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    A self-similar solution for a supernova explosion with allowance for accelerated relativistic particles (2000)
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    Astronomy letters 26 (2000), S. 356-361 
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    ISSN: 1562-6873
    Keywords: supernovae and tsupernova remnants
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A self-similar solution to Sedov’s problem of a strong explosion in a homogeneous medium is generalized to the case of relativistic-particle generation in a supernova remnant; the particles are accelerated by Fermi’s mechanism at the shock front and in the perturbed post-shock region. Self-similarity takes place if the thickness of the prefront is small compared to its radius and if the pressure ratio of the relativistic and nonrelativistic components at the shock front is kept constant. In the presence of relativistic particles, the time dependence of the shock-front radius remains the same as that in their absence, but the plasma parameters in the inner perturbed region change appreciably. The shell of the matter raked up by the explosion is denser and thinner than that in the nonrelativistic case, the relativistic-particle pressure in the central region remains finite, and the nonrelativistic-gas pressure at the explosion center approaches zero. The influence of relativistic particles on the transition to the radiative phase of expansion of the supernova remnant and on its dynamics is studied. It is shown that relativistic particles can decrease several-fold the remnant radius at which the transition to the radiative phase occurs.
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    Optical spectra of four objects identified with variable radio sources (2000)
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    Astronomy letters 26 (2000), S. 339-343 
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    ISSN: 1562-6873
    Keywords: optical spectra ; radio sources
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We obtained optical spectra of four objects identified with variable radio sources. Three objects (0029+0554, 0400+0550, 2245+0500) were found to be quasars with redshifts of 1.314, 0.761, and 1.091. One object (2349+0534) has a continuum spectrum characteristic of BL Lac objects. We analyze spectra of the radio sources in the range 0.97–21.7 GHz for the epoch 1997 and in the range 3.9–11.1 GHz for the epoch 1990, as well as the pattern of variability of their flux densities on time scales of 1.5 and 7 years.
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    Super-Alfvén expansion of a nova shell in the magnetic field of its core (2000)
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    Astronomy letters 26 (2000), S. 362-371 
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    ISSN: 1562-6873
    Keywords: plasma astrophysics ; hydrodynamics and shock waves
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We study the effect of nova magnetodipole fields on the dynamics and structure of ejected shells by using a numerical model based on the kinetic-hydrodynamic description of plasma dynamics. Our calculations show that characteristic nonuniformities appear in the distribution of field and plasma perturbations during super-Alfvén shell expansion in the circumstellar medium.
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    Simulation of a possible process responsible for the loss of the martian atmosphere (2000)
    Springer
    Doklady physics 45 (2000), S. 472-477 
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    ISSN: 1562-6903
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
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    Numerical and analytical investigation of steady-state flow of viscous fluid in a plane confuser (2000)
    Springer
    Doklady physics 45 (2000), S. 467-471 
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    ISSN: 1562-6903
    Source: Springer Online Journal Archives 1860-2000
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    Signal of collisional beatings of polarization of light as a function of the angular momentum of an excited atomic state (2000)
    Springer
    Optics and spectroscopy 88 (2000), S. 7-10 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A comparative study of the beats of circular polarization generated by anisotropic atomic collisions is carried out on the basis of theoretical calculations for the states J=1, 3/2, and 2 of neon atoms and ions excited by monochromatic laser radiation in xenon atmosphere. Contributions made by ordinary alignment and higher polarization moments (octupole orientation and dodecapole alignment) in the collisional generation of orientation and the signal of beatings of circular polarization are compared.
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    Determination of the resolving power of optical systems in the formation of speckle images (2000)
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    Optics and spectroscopy 88 (2000), S. 102-106 
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    ISSN: 1562-6911
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Relations for the calculation of the limiting resolvable spatial frequency of a speckle image of a line mira used as a test object in the determination of the optical power of optical systems are presented. The influence of the speckle structure on the extraction of information about the shape of the object observed from the image recorded is taken into account by using the equivalent modulation transfer characteristic of the optical system than determines the transfer of spatial frequencies of the envelope of the speckle image and the threshold characteristic of speckle noise conditioned by fluctuations of the amplitudes of individual speckles. Conditions, in which the prevailing influence on the quality of the image recorded is exerted by the speckle structure, atmospheric phase distortions, and discretization noise, are determined.
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    One hundred years of observations of the Be star HDE 245770 (the X-ray binary A0535+26/V725 Tau): The end of an active phase? (2000)
    Springer
    Astronomy letters 26 (2000), S. 9-21 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract UBV observations of the X-ray binary system A0535+26/V725 Tau at the Crimean Station of the Sternberg Astronomical Institute in 1980–1998 are presented. Based on our and published data, we analyze the photometric history of the star from 1898. Over a period of 100 years, the star apparently showed all three activity phases (B, Be, Be-shell) of Be stars. We conclude that the X-ray activity of the object is attributable to the 1970–1997 outburst of the Be star due to envelope ejection. The star's colors during the minimum light of 1998 and its 1953–1956 colors (before the outburst) correspond to the spectral type B0–B1 at the color excesses E B-V = 0.74 and E U-B = 0.48, in agreement with the current spectral type O9.7. The minimum light of 1998 and the color excesses are used to determine the colors of the additional radiation, analyze their evolution during the 1973–1997 outburst, and refine the distance to the object (3 kpc). The colors of the additional radiation at maximum light of the star (1973–1980) match the colors of a hydrogen plasma with T e = 1.5 × 104 K which is optically thick in the Balmer continuum. The brightness decline corresponds to a decrease in the optical depth of the plasma; at $$V \simeq 9_.^m 1$$ , it becomes optically thin in the Balmer continuum with T e = 104 K and N e = 1010 − 1012 cm−3. This conclusion is consistent with the model of a circumstellar envelope but is inconsistent with the existence of an accretion disk around the neutron star. All the additional radiation responsible for the optical variability is produced by a single source. The intensity of the Hα emission line at maximum light (1975–1980) is triple its intensity in 1987–1997, when quasi-periodic light fluctuations with P ≈ 1400d were observed [1]. At this time, the line intensity correlated with brightness. The Hα line was in absorption at the minimum of 1998, and, at present, the star's active phase appears to have ended.
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    Determining the period of the long-period activity of the water-vapor maser in W75N (2000)
    Springer
    Astronomy letters 26 (2000), S. 38-48 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We present the results of our study of the H2O maser emission from the source W75N, which is associated with a star-forming region, between November 1994 and March 1999. The observations were carried out with the RT-22 radio telescope of the Pushchino Radio Astronomy Observatory (Lebedev Physical Institute). The maser emission in 1994–1999 can be represented as a superposition of flares of separate components with a duration from two to six months, which occurred mainly in the radial-velocity range 8–17.5 km s−1. We detected a regular drift of the velocity centroid from 13 to 9 km s−1 and an abrupt change in its velocity from 9 to 5 km s−1, which took place at the initial stage of maser activity. Based on the variability of the total H2O flux in all years of our observations of W75N (from December 1979 through March 1999), we conclude that the long-period variability of the water-vapor maser emission has a period of ∼11.5 years. We give arguments that this variability is mainly associated with the most compact group of maser spots, whose positions coincide with the position of the continuum source VLA 2.
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    Features of the Zeeman splitting of levels of the 1snp configurations of helium (2000)
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    Optics and spectroscopy 88 (2000), S. 147-150 
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    ISSN: 1562-6911
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The Zeeman splitting of the fine-structure levels of the 1s2p and 1s4p configurations of neutral helium in a magnetic field is calculated. The strengths of fields of intersection of magnetic sublevels are determined, and the field regions are found in which a constant energy gap between some sublevels is observed. The results are compared with the experimental data available in the literature.
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    Study of the energy level structure for ions of the thallium isoelectronic sequence (2000)
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    Optics and spectroscopy 88 (2000), S. 158-162 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The structure of the energy level diagram for 30 ions of the thallium isoelectronic sequence is studied on the basis of the relativistic Dirac-Fock self-consistent field method with the configuration interaction taken into account. It is discovered that the ground-state configuration and the lowest term change along the thallium isoelectronic sequence: At the beginning of the sequence, the ground-state configuration is 6s 26p, and it becomes 6s 26f beginning from the Cf17+ ion. On the basis of theoretical calculations, the ground-state ionization potentials are determined for each ion. The influence of interaction of the 6s6p 2 configuration with the 6s 26d configuration on the 2 D 3/2, 5/2 levels of the latter was also studied, and values of the fine-structure splitting of the 6s 26p 2 P 0 and 6s 26d 2 D levels were determined for the Tl-like ions considered.
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    RC J0105+0501: A radio galaxy with redshift z≈3.5 (2000)
    Springer
    Astronomy letters 26 (2000), S. 623-627 
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    Keywords: distant radio galaxies
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We study the radio galaxy RC J0105+0501 by using observations with RATAN-600, VLA, and 6-m Special Astrophysical Observatory telescope. The radio source has a structure resembling the FRII type and the spectral index α=1.23; it is identified with a faint galaxy of $$22\mathop .\limits^m 8$$ in R c . The optical object is $$1\mathop .\limits^m 5$$ brighter in V than it is in B and has an extended structure, which we interpret as intense Lyα line emission with redshift z≈3.5 and a continuum depression in the adjacent short-wavelength region. Based on BVR c I c photometry, we also estimated the age of the stellar population of the radio galaxy.
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    The Praesepe open cluster and the galactic distance scale (2000)
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    Astronomy letters 26 (2000), S. 657-659 
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    ISSN: 1562-6873
    Keywords: star clusters and associations ; stellar dynamics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Updated proper motions for 328 probable members of the Praesepe are used to determine the distance to this open cluster by Hertzsprung's geometric method. The cluster distance was found to be r=171±15 pc, which corresponds to the distance modulus $$V_0 - M_V = 6\mathop .\limits^m 16 \pm 0.19$$ . The distance scale for open clusters is discussed.
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    Parametric method in the theory of vibronic spectra of polyatomic molecules: Absorption and fluorescence spectra and structure of styrene in the excited state (2000)
    Springer
    Optics and spectroscopy 88 (2000), S. 182-189 
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    ISSN: 1562-6911
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The excited states and absorption and fluorescence spectra of styrene and β-d 2-styrene are calculated by the parametric method. It is shown that parametric models of these molecules in the excited states adequately describe their real structure and predict the fine structure of their electronic spectra at the quantitative level, which is sufficient for its detailed interpretation and the refinement of parameters of the molecular model by solving inverse problems. In a second approximation (using only one additional parameter), the method provides a more exact calculation of angular deformations of the molecule upon excitation and, in particular, describes characteristic differences in the intensities of low-frequency spectral components in a series of diphenylpolyene-stilbene-styrene. The number of parameters for molecular fragments is small (2 and 3 in the first and second approximations, respectively), and they are the same for a series of related compounds. Compared to direct ab initio calculations, the parametric method yields substantially better results already in the first approximation, and it is more efficient for modeling molecules in excited states and description of their vibronic spectra.
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    Effects of microlensing on parameters of the images seen near the critical curves of gravitational lens galaxies (2000)
    Springer
    Astronomy letters 26 (2000), S. 628-638 
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    ISSN: 1562-6873
    Keywords: gravitational lenses ; microlensing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We investigate the effect of microlensing on parameters of the images of distant sources seen near the critical curves of complex gravitational lenses, which are represented as a sum of compact structures—microlenses (stars, star-like or planet-like bodies) and diffusely distributed matter (dust and gas clouds etc.). The observation of merging, cross-shaped, annular, or arc-shaped source images is an indication that the images are close to the critical curves of gravitational lenses. Our analysis and numerical solution have allowed us to determine the structures of the critical curves and caustics formed by macro-and microlenses, as well as to estimate the characteristic perturbations introduced by microlenses at their various positions relative to the critical curve of a regular gravitational lens. We show that, the closer are the microlenses to the critical curve, the larger is the discrepancy between our results and those obtained previously with standard (linearized) allowance for the effect of a regular gravitational lens.
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    Unsteady mass outflow from Wolf-Rayet stars (2000)
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    Astronomy letters 26 (2000), S. 660-667 
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    ISSN: 1562-6873
    Keywords: sta—variable and peculiar
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We show that hydrostatically equilibrium models for the thin photospheres of helium stars based on new opacities κR (OPAL and OP) can be constructed only for masses M〈5M ⊙. The parameter Г=κL/4πGMc, defined as the ratio of light pressure to gravity, exceeds a critical value of 1.0 for larger masses, which must result in mass outflow under light pressure. This mass limit matches the observed lower limit for the masses of Wolf-Rayet stars (M WR〉5M ⊙)), which is an additional argument that the Wolf-Rayet stellar cores are actually helium stars. By solving the equation of radiative transfer in extended atmospheres, we construct a semiempirical model for a WN5 star (M WN5=10M ⊙)) with a helium core and an expanding envelope, whose physical and geometric parameters are known mainly from light-curve solution for the eclipsing binary V444 Cyg (WN5+06): outflow rate $$\dot M \approx 1.0 \times 10^{ - 5} M_ \odot yr^{ - 1} $$ , terminal velocity V ∞≈2000 km s−1, and expanding-envelope optical depth τenv≈25. The temperature at the outer boundary of the photosphere of a helium star surrounded by such an envelope is approximately 130 kK higher than that in the absence of an envelope, being T ph≈240 kK. Because of the high temperatures, the absorption coefficients at the corresponding photospheric levels are smaller than those in models with no envelope; therefore, the photosphere turns out to be in hydrostatic equilibrium and stable against light pressure (Гmax≈0.9). As a way out of this conflicting situation (an expanding envelope together with a hydrostatically equilibrium photosphere), we propose a model of discrete mass outflow, which is also supported by the observed cloudy structure of the envelopes in this type of stars. To quantitatively estimate parameters of the nonuniform outflow model requires detailed gas-dynamical calculations.
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    The orbit of the nearby low-mass binary Gliese 600 (2000)
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    Astronomy letters 26 (2000), S. 668-671 
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    ISSN: 1562-6873
    Keywords: stars—properties ; classification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We have computed a combined spectroscopic-interferometric orbit for the nearby binary Gliese 600 discovered by us. The orbital period is 2.78 years, and the semimajor axis is 100 mas (0.1″). Its M0 V components are almost identical and have a mass of 0.5M ⊙. The mass ratio is uncertain because of the low radialvelocity semiamplitude (7 km s−1) associated with the low orbital inclination (37°). The orbital parallax of the binary (52±11 mas) matches its dynamical and photometric parallaxes but differs significantly from the Hipparcos parallax (44.3±1.6) mas; the latter was probably distorted by the orbital motion that was not taken into account.
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    Tests for spatial isotropy of three thousand gamma-ray bursts found in BATSE archival data (2000)
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    Astronomy letters 26 (2000), S. 672-678 
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    Keywords: gamma-ray bursts
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We apply isotropy tests to our new uniform catalog of cosmic gamma-ray bursts (GRBs) (Stern and Tikhomirova 1999). The catalog contains trigger and nontrigger bursts found in 1024-ms BATSE records over seven years. Based on this catalog, we confirm isotropy of the GRB spatial distribution for a sample that surpasses previous samples in size (2934 bursts) and in achieved threshold (fluxes down to 0.1 phot. cm−2 s−1, which is a factor of ∼2 lower than the BATSE trigger threshold). We also confirm that there is no excess of bursts toward the galaxy M 31.
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    Special features of spectral and luminescent properties of squarilic dyes in polymer matrices (2000)
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    Optics and spectroscopy 88 (2000), S. 352-358 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A study was made of spectral and luminescent properties of a squarilic dye on the basis of 1,3,3-trimethyl-3H-indoline in comparison with the cationic polymethine dye representing a derivative of the same heterocycle. The squarilic dye was introduced into polymer films of poly-N-epoxypropylcarbazole, which is capable of bearing photoproduced charges, and polystyrene, which lacks this ability. Luminescence spectra of films with different dye concentrations at temperatures of 4.2 and 300 K were studied. Spectral and luminescent properties of squarain in both types of polymers were found to be determined by the dye tendency to aggregation. For poly-N-epoxypropylcarbazole, this tendency is less pronounced than for polystyrene, which is associated with the enhancement of specific solvation of a bipolar squarain molecule by polar groups of poly-N-epoxypropylcarbazole. The structure with an angle between chromophore directions of 180° is shown to be the most likely spatial structure of associates. The advantage of this structure is that it is stabilized at both ends of bipolar molecules by electrostatic attractive forces between opposite charges.
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    Orientation effects in anomalous elastic scattering of polarized X-rays by a linear molecule (2000)
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    Optics and spectroscopy 88 (2000), S. 365-367 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A strong orientation effect is theoretically predicted in a suggested modified experiment on anomalous elastic scattering of linearly polarized X-rays by free oriented in space HF and HCl molecules near the ionization threshold of the 1s molecular orbital. The analytic expression for the form factor of a linear molecule is determined for the case of one-center nonrelativistic representation of the wave functions of molecular orbitals.
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    Self-induced transparency in a resonance medium with the dipole-dipole interaction (2000)
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    Optics and spectroscopy 88 (2000), S. 387-389 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Propagation of a pulse of self-induced transparency in a resonance medium is discussed for the case when it is necessary to take into account the direct electric dipole-dipole interaction between atoms. An equation for the envelope of a wave packet—the sine-Gordon equation—is obtained for the case of durations short compared to ω 0 −1 (ω0 is the transition frequency). The dependence of the velocity and the amplitude of the soliton on the magnitude of the dipole-dipole interaction of atoms is examined in the adiabatic approximation.
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    Gyrotropy of molecular crystals with vacancies (2000)
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    Optics and spectroscopy 88 (2000), S. 448-452 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A microscopic analysis is made of the gyrotropy of molecular crystals with vacancies. For impurity-free systems with a primitive lattice, the concentration dependence of rotatability in two frequency regions is studied.
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    Scattering of laser radiation by multifractal biological structures (2000)
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    Optics and spectroscopy 88 (2000), S. 444-447 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Scattering of laser radiation by structured biotissues—histological mounts of bony and muscular tissues and skin, are studied.
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    Light scattering by multilayer ellipsoids in the Rayleigh approximation (2000)
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    Optics and spectroscopy 88 (2000), S. 441-443 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A problem of light scattering by multilayer confocal ellipsoids is solved in the Rayleigh approximation. The electric field of a light wave is assumed constant and a set of Laplace equations with the corresponding boundary conditions is considered. The final expression for the polarizability of a particle is represented in the matrix form (2×2 matrices) in terms of parameters of a nucleus and subsequent layers. Numerical calculations of the scattering and absorption efficiencies of small multilayer spheres obtained using the exact (the generalization of the Mie theory) and approximate solutions well agree with each other.
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    Electronic Resource
    Electronic Resource
    Suppression of background transmission of interference filters (2000)
    Springer
    Optics and spectroscopy 88 (2000), S. 455-458 
    Details
    ISSN: 1562-6911
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The possibility of manufacturing interference filters with the transmission coefficient no less than 90% in fixed UV, visible or near IR spectral regions and completely opaque at longer wavelengths is shown. The operation of the filter is based on the method of residual rays. Angular dependences of the filter transmission bandshape on the parameters of multilayer coating, such as the thickness, refractive indices, and the number of the layers, are analyzed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1134/1.626818
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