Natural electron oscillations in granular aluminum films deposited on rough surfaces of NaCl and KCl single crystals

Granular aluminum films deposited on rough surfaces of NaCl and KCl single crystals form a two-layer coating. In the lower layer, a low-frequency band of plasma resonance is excited due to the joint action of a light-wave field and a field induced by granules-dipoles. In a small amount of granules of the upper layer isolated from each other, a high-frequency band with a frequency ω₀ of natural electron oscillations in the granules is excited. Using the measured frequencies ω₀ and the known dielectric constants of NaCl and KCl, a plasma frequency of aluminum is calculated that agrees well with the known plasma frequency of solid samples. Kharkov State University, 4 Svoboda Sq., Kharkov, 310077, Ukraine. Translated from Zhurnal Prikladnoid Spektroskopii, Vol. 66, No. 6, pp. 853–856, November–December, 1999.     

Radio wave scattering by dust-acoustic waves in a dusty space plasma

It is shown that weakly damped dust-acoustic modes result in an additional maximum in the scattering spectrum. The possibilities of determining dusty plasma parameters from radio wave scattering experiments in space are discussed. Radioastronomical Institute of the Ukrainian National Academy of Sciences, Kharkov. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 40, No. 9, pp.1086–1090, September, 1997.     

Interpretation of the soret band of porphyrins based on the polarization spectrum of N-methyltetraphenylporphin fluorescence

Low-temperature (77 K) absorption, fluorescence, and fluorescence-excitation spectra and the fluorescence polarization spectrum for N-methyl-meso-tetraphenylporphin (N-methyl-TPP) are measured. Based on the polarization spectrum the absorption spectrum in the visible region (a “generic” porphyrin spectrum) is interpreted. In particular, it is shown that the fifth absorption band (the “Longo band”) that manifests itself in some porphyrins is a Q_y(0–2) band and does not belong to the individual electron transition. Emphasis is placed on the region of the Soret band. It is inferred that at least two allowed electron transitions (G →B_x and G→B_y) polarized mutually perpendicularly manifect themselves in this region. The interpretation of the Soret band of porphyrins [2] that attributes this band to one electron transition G→B_x is thereby rejected. This interpretation is confirmed by computer modeling of the polarization spectrum. Special features of the experimental polarization spectrum are explained by a more developed vibrational structure and, possibly, a larger half-width of the B_x band than the half-width of the B_y band. The contribution of the states of intramolecular charge transfer to the formation of the Soret band is discussed. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 1, pp. 65–72, January–February, 1999.     

Photoluminescence spectra of copper-based planar nanostructures

We have studied the luminescence of planar nanostructures based on amorphous copper, excited by a low-intensity source in the UV region of the spectrum. We have shown that it is dependent on the packing density of copper granules on the surface of the quartz substrate, the presence of chains of granules, the optical properties of the surrounding medium, and the oxidation time. The observed maxima at the wavelengths of 400 nm and 520 nm correspond to luminescence of the quartz and copper oxide Cu₂O. The maximum at 650 nm is located in the region of plasma resonances of the oxidized copper chains and aggregates, and is enhanced in the “hot spot” region near the surface of interacting copper particles. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 4, pp. 510–515, July–August, 2006.     

Modulation response of dynamic single-mode quantum-well heterolasers in the 1.5 μm range

Numerical modelling is used to study the effect of tuning the laser output over the gain bandwidth on the modulation response of GaInAs–GaInAsP quantum-well heterolasers for different modulation frequencies of the pump current. It is found that the maximum frequency bandwidth of the response band and the greatest feasibility of high speed modulation for transmission of signals in information systems are achieved in the center of the gain band. Raising the dc component of the pump current increases the response bandwidth. For typical parameters of this system (near 1.5 μm) the maximum response bandwidth can approach ≈40 GHz. For certain parameters, the amplitude-frequency characteristics of the heterolasers have two local maxima: one at low frequency corresponding usually to a resonance for the 1/2 subharmonic and one at high frequency, for the fundamental resonance.     

Effect of polarization and coherence of low-intensity optical radiation on fish embryos

  We have shown that brief exposure of sturgeon embryos (fertilized roe) in the organogenesis stage to low-intensity radiation in the visible region of the spectrum can have a long-term effect on embryonic and post-embryonic development of the fish, detectable 50 days after the irradiation procedure. The biological effects (size-weight characteristics and hardiness parameters of the fish relative to unfavorable habitat conditions) induced by linearly polarized emission from a monochromatic laser source (helium-neon laser, λ = 632.8 nm, Δλ ≈ 0.02 nm) and a quasi-monochromatic light-emitting diode (LED) source (maximum in emission spectrum λ = 631 nm, Δ λ = 15 nm) are practically the same. Going to broadband linearly polarized radiation (λ = 420–800 nm) is accompanied by a decrease in the biological effect. From the results of studies of the effect on embryos from linearly polarized and unpolarized radiation from an LED source and also the effect of linearly polarized, circularly polarized, and unpolarized radiation from a helium-neon laser, we concluded that the type of polarization is of critical importance in realization of the biological effect of radiation. In this case, the maximum stimulating effect (on the size×weight characteristics and the hardiness parameters for juvenile fish) is observed on exposure to linearly polarized radiation; the photobiological effect induced in the same dose range by light with natural polarization (i.e., unpolarized) is significantly less pronounced; the stimulating effect of circularly polarized radiation occupies an intermediate position. Based on the presented data and also on data obtained previously, we conclude that among the resonant and nonresonant photophysical processes (orientational effect of light, effect of gradient forces, dipole-dipole interactions, thermooptic processes) capable of inducing photobiological effects dependent on such laser-specific characteristics as polarization and coherence, the determining influence in the processes studied in this work comes from the orientational effect of light and dipole×dipole interactions. And the orientational effect can appear for anisotropic media with liquid-crystal type ordering (especially domains in membranes and multiple-enzyme complexes) both under conditions when there is no resonant absorption and for weakly absorbing structures, and can initiate a change in their conformations and accordingly their functional characteristics. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 6, pp. 843–858, November–December, 2008.     

Features of the dispersion characteristics of nonuniform plasma waveguides in a longitudinal magnetic field

We study the features of the dispersion curves and field structures of the fundamental axisymmetric mode of nonuniform layered plasma waveguides in a longitudinal magnetic field. It is shown that the presence of sharp boundaries between layers leads to the appearance of additional branches of the dispersion curves in the frequency range ω _Be < ω < ω_UH(0), where ω_Be is the electron gyrofrequency and ω_UH(0) is the upper-hybrid resonance frequency for the near-axis region of a nonuniform waveguide. The fields of eigenmodes corresponding to these branches comprise resonance structures near the sharp plasma-density variation at which the upper-hybrid resonance conditions are satisfied and plasma waves are excited. The frequency interval of such a branch is limited by the resonant frequencies of the neighboring uniform layers. It turns out that in the case of a strong magnetic field ({ie392-01}, where ω_p is the plasma frequency having the value {ie392-02} in the near-axis region of a nonuniform waveguide), the fundamental-mode field is localized in the near-axis region of a nonuniform waveguide, whereas in the opposite case {ie392-03}, the maximum wave fields are localized in either the upper-hybrid resonance region or the outer (near-boundary) layer of the waveguide if there is no resonance region. It is found that the whistler (helicon) contribution to the field structure of the fundamental axisymmetric mode is very small for narrow nonuniform waveguides (b < λ₀, where b is the waveguide radius and λ₀ is the wavelength in free space) if the plasma density on the axis is high compared with the cutoff density {ie392-04}. We present one of the possible explanations for the effect of narrowing of the plasma channel of a high-frequency whistler-range discharge with distance from a source in the increasing magnetic field. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 51, No. 5, pp. 434–446, May 2008.     

Radiative characteristics and kinetics of processes in low-pressure gas-discharge lamps based on a mixture of helium and iodine vapors

The UV radiation of glow- and capacitive-discharge lamps based on mixtures of inert gases with iodine vapors are optimized in the spectral range of 175–360 nm, in which working helium-iodine mixtures of different compositions are used. The most intense spectral lines in the bactericidal region of the spectrum were the atomic lines of iodine (183.0, 206.2 nm), and in the region of 320–360 nm, emission of the spectral band of an iodine molecule prevailed with a maximum at λ = 342 nm. For a capacitive lamp with a casing opaque in the spectral range λ < 250 nm, the main part of the plasma emission power is concentrated in the A′-D′ band of an iodine molecule with a maximum at 342 nm. The emission brightness of this lamp is optimized in iodine molecule transitions depending on the partial helium pressure. We present the results of simulating the kinetics of processes in a glow-discharge plasma in mixtures of He, Xe, and iodine vapors. We establish the dependence of the main part of the emission intensity of the 206.2 nm spectral line of an iodine atom and the 342 nm band of an iodine molecule on the helium pressure in a glow-discharge lamp operating on a He-I₂ mixture.     

Phonon-Assisted Photoluminescence in a Spherical Nanocrystal

Using the matrix density in the representation of path integrals for an electron, the multiphoton nonlinear absorption light coefficient in the second order of interaction energy with polar optical phonons is derived. This coefficient describes any electron interaction mechanism with phonons. From the interaction mechanism, the main role is played by dimensional resonance when the electron continuously absorbs energy from the field as a result of synchronizing its oscillation with the field. This dimensional resonance is possible when the frequency characterizing the laser field is a multiple of the phonon frequency. Whether a photon is absorbed or emitted, the initial level from where the transition occurs defines the temperature dependence. The absorption spectrum has the form of stripes whose intensity depends on the resonance character. The most pronounced absorption is at the triple resonance, where values of radiation and oscillatory and optical phonon frequencies are equal. __________ Published in Zhurnal Prikladnoi Spektroskopii, Vol. 72, No. 5, pp. 654–659, September–October, 2005.     

Effect of current modulation depth on the response of single-mode quantum-well heterolasers in the region of 1.5 μm

Numerical simulations are used to study the effect of pump current modulation depth on the response of quantum-well GaInAs–GaInAsP heterolasers at different lasing frequencies within the gain band as a function of the excess above threshold. It is shown that the amplitude-frequency characteristics of these laser emitters generally contain two local maxima. The low frequency maximum usually corresponds to a resonance for the 1/2 subharmonic and the high frequency maximum, to the fundamental. As the modulation depth is increased, the fundamental frequency decreases, while the resonance frequency for the 1/2 subharmonic can change monotonically or not. The behavior found here can be used to develop quantum-well heterolasers with specified modulation parameters.     

On kinetic effects in the ionosphericF-region modified by powerful radio waves

We consider effects related to acceleration of electrons by high-frequency plasma turbulence in the ionospheric F-region modified by powerful radio waves. The threshold of avalanche growth of the number of accelerated particles due to additional ionization is determined for pump-wave frequencies far from the multiple cyclotron resonance. The steady-state density of the accelerated electrons is found for the above pump-frequency values taking into account both turbulent trapping in the accelerating layer due to scattering of plasma waves and the return of electrons to this layer due to collisions. If the pump wave frequency is close to the multiple cyclotron resonance, fast electron distribution with significant transverse anisotropy is formed. Relaxation of this distribution due to collisions with charged particles outside the accelerating layer leads to the appearance of a maximum over transverse velocities in the tail of the distribution function. We propose a generation mechanism for the broad upshifted maximum feature in the spectrum of stimulated electromagnetic emission, which is related to the cyclotron instability of the accelerated electrons. The instability occurs in the double-resonance region in which the pump frequency is close to both the upper-hybrid and multiple-cyclotron frequency. Radiophysical Research Institute, Nizhny Novgorod, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 42, No. 7, pp. 651–669, July 1999.     

Raman spectral analysis of the intermolecular hydrogen bond in bromoform

The maximum of the perpendicular polarized component of the Raman spectrum of the C−H mode in liquid bromoform shifts by 1.5 cm⁻¹ toward higher frequencies from the maximum of the parallel polarized component. A high-frequency shift of this band is noted in solution with nitromethane and nitrobenzene, and the shape of the band becomes more complex. The result is attributed to superposition of the associate lines in the mixture (the high-frequency component) and the monomer line. There are indications that the 537 cm⁻¹ band of bromoform in a mixture with the same solvents and with pyridine has a doublet character. When CHBr₃ is dissolved in a neutral solvent such as heptane, both bands exhibit normal behavior, the widths of the lines decreasing presumably because of an increase in the vibrational relaxation time. A. Navoi State University, Samarkand. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 90–94, December, 1998.     

Modulation Characteristics of Tunable Quantum-Well Heterolasers at the Radiation Frequency Tuning

The influence of the tuning of the radiation frequency of quantum-well heterolasers within the limits of their amplification band on the output laser radiation parameters at different frequencies of pump-current modulation has been numerically simulated using two optical models of an active medium under the assumption that the excess of the invariable component of the pump current over its threshold value at any point of the amplification band is constant. It has been established that the amplitude-detuning characteristics of the lasers studied are linear at high current-modulation frequencies and nonlinear at medium ones. The behavior of the nonlinear spectral response of a laser diode is explained by its multiresonance structure and is mainly determined by the ratio between the pump-current modulation frequency and the maximum resonance frequency of the laser. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 72, No. 4, pp. 473–478, July–August, 2005.     

Inelastic light scattering by a two-dimensional electron system with Rashba spin-orbit coupling

Inelastic light scattering by a two-dimensional system of electrons in a conduction band with Rashba spinorbit coupling is studied theoretically for the resonance case where the frequencies of the incident and scattered light are close to the effective distance between the conduction band and spin-split band in a III–V semiconductor. It is shown that, in contrast to the case of no spin-orbit coupling, the spectrum of the scattered light exhibits a plasmon peak even for strictly perpendicular polarizations of the incident and scattered light. There exists a configuration where the scattering spectrum exhibits features originating from single-particle transitions only. Furthermore, it is shown that, for the general case of elliptic polarizations of the incident and scattered light, the amplitude of the plasmon peak depends on the sign of the effective Rashba spinorbit coupling constant and the signs of the phases of the polarization vectors. This fact can be used to determine the sign of the Rashba constant.     

Spectral-luminescence properties of a norbornene-substituted tetraazachlorin and its metal complexes

The spectral-luminescence properties of a tetraazachlorin derivative with a norbornene fragment annelated to a reduced pyrrole ring and its complexes with zinc and palladium have been studied at 293 and 77 K. For the norbornene-substituted free base, differences in fluorescence from unsubstituted tetraazachlroin and its dibenzobarrelene-substituted analog are found. The fluorescence lifetime is observed to rise by ∼7 times for the free base and by ∼1.6 ties for the Zn complex on going from 293 to 77 K. An essential dependence of the photophysical parameters on the nature of the solvent is noted. The fluorescence polarization spectrum of the norbornene-substituted tetraazachlorin reveals in the Soret band region at least four electronic transitions. For the Pd complex, weak phosphorescence in the near IR region has been detected; the 0–0 band maximum is at 990 nm and the singlet–triplet interval amounts to 5800 cm^–1, which is larger by 400 cm^–1 than for Pd tetraazaporphine. The quantum yields of the photosensitized formation of singlet oxygen have been determined using a relative luminescence method.     

Tamm states of carbon nanotubes

The fine structure of the π-electron spectrum of semi-infinite carbotubulenes (cylindrical graphene tubes) is investigated. Together with closed short-diameter tubelenes, open nanotubes whose terminal fragments contain heteroatoms are studied. Algebraic equations are obtained for the one-electron energy levels corresponding to wave functions localized on a terminal fragment. It is shown that Tamm energy levels, lying in either the band gaps or the continuous spectrum (resonance states), can exist in the systems studied. Pis’ma Zh. éksp. Teor. Fiz. 63, No. 8, 588–593 (25 April 1996)     

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在理想条件下,为了研究等离子体参数、填充率、入射角度和介质层相对介电常数对一维三元磁化等离子体光子晶体的禁带特性的影响,用由传输矩阵法计算得到的TE波任意角度入射时的左旋极化波(LCP)和右旋极化波(RCP)的透射系数来研究其禁带特性。结果表明,仅增加等离子体碰撞频率不能实现禁带宽度的拓展,改变等离子体频率、填充率和介质层的相对介电常数能实现对禁带宽度和数目的调谐。改变等离子体回旋频率能实现对右旋极化波的禁带的调谐,但对左旋极化波的禁带几乎无影响。入射角度的增大使得禁带低频区域带宽变大,而高频区域带宽则是将先减小再增大。     

Analytical model for the behavior of electric fields in a collisional low-pressure RF discharge

A simple analytical model is presented making it possible to determine the amplitudes and phases of the rf field in the electrode sheaths and quasineutral plasma of an rf discharge in the presence of electronneural collisions. The collisional case ω≪ν is considered in detail. Measurements are also made of the electron temperature, plasma density, thickness of the electrode sheaths, and rf field amplitude in the quasineutral plasma of an rf discharge in argon. The rf field amplitudes predicted by this model are in satisfactory agreement with both our experimental data and the results of theoretical calculations of other authors. Kharkov State University, Kharkov. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, Vol. 41, No. 12, pp. 31–38, December, 1998.     

Ultrahigh-energy cosmic rays: Possible origin and spectrum

The complicated shape of the cosmic ray spectrum recorded by giant arrays in the energy range 10¹⁷–10²⁰ eV is analyzed. It is shown that in the energy region ∼10¹⁸–10¹⁹ eV the spectrum probably coincides with the injection spectrum whose exponent is equal approximately to 3.2–3.3. The flatter component in the energy region (3.2–5.0)×10¹⁹ eV is due to braking of extragalactic protons on primordial photons (the cosmic background radiation). At energies exceeding 3.2×10¹⁹ eV the spectrum does not have a blackbody cutoff. The possibility of determining the distances at which cosmic rays originate and investigating the evolution of their sources on the basis of ultrahigh-energy cosmic ray data is discussed. Zh. éksp. Teor. Fiz. 113, 12–20 (January 1998)     

Effect of exposure of sturgeon roe to low-intensity laser radiation on the hardiness of juvenile sturgeon

We present data on the effect of polarized laser radiation in the near IR region of the spectrum with wavelength 808 nm on the resistance of juvenile sturgeon to oxygen deficiency in the habitat when the fertilized roe are briefly exposed to radiation in the organogenesis stage. The magnitude of the stimulating effect depends on the exposure time (t) and power density (P) of the radiation and also on its modulation frequency (F). For optimal irradiation parameters (cw mode, P = 2.9 mW/cm², t = 60 sec), the hardiness of the juveniles increases by a factor of ∼1.5 compared with the control group. The maximum differences in the sensitivity of embryos to cw and pulsed radiation are observed for F = 1 Hz; as the modulation frequency increases up to F = 50 Hz, the magnitude of the photobiological effect approaches a level typical for cw exposure. We show that the duration of the dark period (pause time) between pulses is the critical parameter determining the dependence of the stimulating effect on the modulation frequency. We discuss questions concerning use of the indicated physical factor in the technology for raising sturgeon under industrial fish farming conditions. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 2, pp. 233–241, March–April, 2008.