Segregation of Components as a Result of High‐Power Laser Irradiation of Heterogeneous Condensed Media

The effects of periodic segregation of components in metastable (supercooled or supersaturated) binary alloys in the course of kinetic phase transformations as a result of laser irradiation of heterogeneous systems were studied analytically. Nonlinear processes of temporal and spatial selforganization of concentrationrelated structures were simulated using (i) a selfconsistent system of timedependent twodimensional equations for the distribution function for the sizes and spatial coordinates of the newphase particles and (ii) balance equations for the temperature and concentration of dissolved components; the latter equations account for nonlinearity of the particlesource function, sinks, for dependences of the phasetransition temperature on the surface curvature of particles and on the concentration of components, and for diffusive motion of particles in space. The domain of existence for the instabilities under consideration and the characteristics of the formed crystallizationrelated periodic structures are determined. It is established that nanoclusters formed during supersaturation of crystallizing material may play an important role in generation of selfoscillatory crystallization modes. Hydrodynamic aspects of liquidphase concentrationrelated stratification in heterogeneous systems based on immiscible components are considered.     

Influence of Solvent Polarity and Viscosity on Nonradiative Processes in Oligothiophenes with Intramolecular Charge Transfer

By the methods of luminescence, picosecond spectroscopy, and quantumchemical calculations the mechanisms of electron excitation energy deactivation in some oligothiophenes with intramolecular charge transfer depending on the solvent polarity and viscosity have been investigated. While for 2Npiperidino5(2,2dicyanovinyl)thiophene (PDCVT) the main channel of nonradiative deactivation is the transition to a lower intermediate state with a twisted double bond controlled by the medium viscosity, in the case of (E){2[25piperidino2thienyl]6(trifluoridemethyl)4H4pyranylidene}propanedinitryl (PTFDN) fluorescence quenching is initiated by the solvent polarity. For two other oligothiophenes, 2Npiperidino5cyanothiophene (PCT) and 2Npiperidino5cyanoterthiophene (PCTT), differing in the length of the thiophene chain, we have revealed, along with the effective quenching of fluorescence in shortchain PCT (independent of the solvent polarity and viscosity), an increase in the radiation capacity in PCTT with increasing polarity of the solvent. The possible mechanisms of nonradiative deactivation in the investigated oligothiophenes are discussed.     

Heterogeneous Chemiluminescence of Crystal Phosphors on X‐Ray or UV Irradiation

Using a highvacuum assembly with molecular beams and setups with an implemented atom probe, we investigated atomic and molecular adsorption luminescence of the oxides CaOBi and MgO in O and O₂ beams and also radicalrecombination luminescence excited by H and O atoms in ZnS and in ZnS,CdS samples activated with silver, copper, and the rareearth element Tm. It is established that exposure to UV light and xray radiation of the CaOBi, MgO, and ZnSTm samples, where the mechanism of direct excitation of heterogeneous chemiluminescence (HCL) is realized, does not influence the characteristics of the heterogeneous chemiluminescence, whereas similar exposure of the ZnS,CdSCu,Al and ZnS,CdSAg samples and of selfactivated ZnS, in which the excitation of heterogeneous chemiluminescence is due to the ionization of the lattice, leads to an increase in the intensity of heterogeneous chemiluminescence up to five orders of magnitude. The mechanisms of the phenomenon are considered.     

Photostability of Molecules of Aromatic Amines in a Polymeric Matrix

In the temperature range T = 5–295 K, the spectralluminescent properties and curves of thermostimulated luminescence (TSL) of molecules of triphenylamine (TPA), trirtolylamine (TTA), triranisolamine (TAA), and N,N'diphenylbis(3methylphenyl)(1,1'biphenyl)4,4'diamine (TPD) in polystyrene and 4Brpolystyrene matrices have been investigated. It has been found that photoirradiation at room temperature in the region of the lowest electron transition of molecules leads to a decrease in the intensities of the luminescence, photoluminescence, and TSL bands, as well as to the formation of new deep traps for charge carriers. At equal irradiation doses these changes in TPD are noticeably less pronounced than in TPA, TTA, and TAA. The higher photochemical stability of TPD molecules compared to TPA, TTA, and TAA is attributed to the difference in the mechanisms of nonradiative deactivation of the triplet states of molecules.     

Spectral Properties of the Radiation of Injection Lasers at Prethreshold Excitation Levels

The spectral properties of the radiation of injection lasers at low (prethreshold) levels of excitation were investigated experimentally by the method of optical heterodyning of the Doppler signal and also with the use of a KSVU23 spectral setup. It is established that these lasers may serve as sources of the optical radiation of TE and TMpolarizations with a retuned length of coherence within the range 1–10 mm in spectrometric facilities of photoheterodyne type. A procedure for determining the inversion current in an injection laser is suggested.     

Monochromatization of synchrotron radiation for nuclear resonant scattering experiments

An introduction to monochromatization of synchrotron radiation in the energy range of 5–30 keV is presented for applications involving nuclear resonant scattering. The relevant relationships of the dynamical theory of Xray diffraction are used to explain basic concepts of monochromatization. These relations are combined with raytracing techniques to design highenergyresolution monochromators. Transmissionoptimized and energyresolutionoptimized designs that achieve high energy resolutions (10⁶)< E/E < 10⁸) are discussed separately. Practical silicon monochromators of both types are presented for a variety of nuclear resonances in this energy range.     

Systems Approach to Optimization of the Regimen of Photodynamic Therapy of Solid Sarcoma M-1 Using the “Fotosens” Preparation as Example

A systems analysis of the interaction between objects (tumor, healthy tissue, radiation, and photosensitizer of the singlet state of oxygen) involved in photodynamic therapy was carried out. A schematic diagram of the biologically significative processes proceeding under these circumstances was proposed. This schematic diagram can serve as a basis for a systems approach to the optimization of photodynamic therapy. The efficiency of the systems approach in photodynamic therapy was demonstrated using Fotosens and Khlorin S preparations, carotene, and dodecaprene -carotene in biological experiments on Wistar rats and mouses inoculated for the solid sarcoma M-1.     

FIR Photonic Microwave Filter Design Employing Simulated Annealing Algorithm

Photonic microwave filters are important parts of fiberoptic microwave/millimeter wave processing systems. In this paper, the synthesis problem of fiberoptic FIR microwave filters is addressed and a novel method for designing photonic microwave filter employing a simulated annealing (SA) algorithm is proposed. The design problem of photonic microwave filter can be reduced to be a multivariable function optimization problem, which can be solved by a simulated annealingbased algorithm. As an illustration of the application of SA to photonic microwave filter design, the synthesis of an optimizedFBGbased photonic microwave filter is discussed. Numerical results show that the global minimum finding capability of SA makes it be an efficient way to design the photonic microwave filter. Numerical results also demonstrate that the proposed method can be applied to design different filtering systems with different constraints.     

Quantum Theory of Self‐Phase Modulation of Ultrashort Light Pulses in a Medium with Inertial Electronic Nonlinearity

We develop a systematic quantum theory of formation of ultrashort light pulses in a squeezed state at selfphase modulation. The response time of the electronic Kerr nonlinearity of the medium is accounted for and the dispersion of linear properties of the medium is described in first approximation. The theory uses the approach based on the momentum operator for the electric field. The response function of the nonlinearity is contained in the interaction operator. The results obtained are valid when the pulse duration is far greater than the nonlinear response time and the carrier pulse frequency is offresonance. It is established that the instantaneous spectral distribution depends quasistatically on the pulse form. In the general case, the spectral distribution of the quadraturesqueezed component is defined by both the response time of the nonlinearity and the magnitude of the nonlinear phase addition. It is also shown that the frequency at which suppression of quantum fluctuations is greatest can be controlled by adjusting the phase of the initial coherent light pulse. It is found that, by registering the quadraturesqueezed pulse using a balanced homodyne detector, the squeezing effect can be efficiently measured if the timedependent phase of the heterodyne pulse obeys a specific dependence defined by the pulse form. The spectral photonnumber distribution of the quadraturesqueezed pulse is studied, and the photon antibunching effect is found for the photon number in a limited spectral band.     

Double quantum transitions in paramagnetic resonance

The theory of double quantum transitions of the M=±2 type, with regard to inhomogeneously broadened spin systems is studied in this paper with the approximation ²T₂T₃ 1. We suppose that the inhomogeneous broadening is formed by an inhomogeneous crystal field. The obtained results describe the magnitude of absorption as a function of the h.f. power and also describe the shape of the absorption curve. It is demonstrated that in inhomogeneously broadened spin systems the absorption curve of double quantum transitions has the form of the difference of two different Lorentz's curves and that at the saturation ( ²T₂T₁ 1) the absorption increases with the cube of the h.f. field intensity. The shape of the curves is expressed by means of phenomenological relaxation constants of the system.

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M=±2 ²T₂T₃ 1. , - . . , ( ²T₂T₁ 1) . .

     

Influence of IR Radiation on the Electron Mobility in Submicron Layers of GaAs

The influence of optical radiation near the impurity absorption band on the electron mobility in submicron doped gallium arsenide layers formed on semiinsulating substrates is investigated. To determine the lowfield mobility of carriers, a method is used which is based on measurements of the mutual conductance and series resistances of a fieldeffect transistor at low sourcetodrain voltage. It has been established that the electron mobility increases under IR illumination as a consequence of decrease in electron scattering, and this is related to the photoneutralization of deeplying chrome acceptors.     

Absorption Spectra of Excited Ruby Crystals

We have investigated the absorption spectra of excited laser single crystals of ruby. The longlived increase in absorption depending on the degree of excitation is observed in optically excited crystals of ruby in a wide spectral range. Moreover, in the absorption spectrum of a postexcited ruby we discovered the excitationinduced longlived kinetic instability, namely, the noiselike quasiline component variable in time and over the spectrum and imposed on the smooth spectral curve.     

Conditions for Obtaining Stimulated Radiation in Thin‐Film Organic Electroluminescent Structures

This paper analyzes the possibilities of obtaining induced radiation in singlelayer organic electroluminescent structures on the basis of the proposed model of luminophor molecule excitation by hot electrons emitted from the cathode as a result of the tunnel effect. Numerical calculations of the kinetic, spectral, and energy characteristics of radiation in the regime of singlepass superluminescence and in the presence of positive feedback have been made. It has been concluded that, in principle, it is possible to obtain in such systems induced radiation at actually attainable values of the applied electricfield strength, and the conditions for this have been analyzed.     

Poloidal Magnetic Field Measurements in a Reversed Field Pinch Plasma by a Far‐Infrared Polarimeter

A multichannel farinfrared (FIR) polarimeter has been installed in RFX, a Reversed Field Pinch (RFP) plasma experiment, to measure the poloidal magnetic field profile. The polarimeter uses a CH₃OH FIR laser operating at =118.8 m. Faraday rotation measurements on five of six parallel diagnostic chords are used in preliminary investigations of poloidal field profiles. The experimental results are generally found in good agreement with the &p model predictions. The choice of the profile of = ₀ j·B/B² is discussed. For the reconstruction of the magnetic field profiles a numerical filamentary current equilibrium code is described, where polarimetric data are included as constraints. An alternative method based on the bestfit of a threeparameter profile to the polarimetric data is also reported. Both methods provide reliable reconstructions of the plasma magnetic field and the results indicate the existence in RFX of hollow profiles.     

Calculation of the Tautomeric Properties of 3‐Formyl‐Tetrinic Acid by the ab initio and DFT Methods

We have carried out a nonempirical quantumchemical calculation with full optimization of the geometry of all theoretically possible tautomeric forms of 3formyltetrinic acid (FTRA) according to the Møller–Plesset secondorder perturbation theory with the use of a 6–31G(d) double zeta basis set. The correlation corrections to the total energy of molecules for optimized geometric configurations were calculated in the 631G(d,p) basis. All the possible tautomeric forms of FTRA and the harmonic vibrational frequencies were also calculated within the density functional theory (DFT) with the use of the Perdew–Burke–Ernzerhof (PBE) functional in a threeexponent basis. It is shown that FTRA in vapors (in the perfect gas approximation) exists in the form of a mixture of three enol forms, among which two exoforms predominate. The frequencies and forms of normal vibrations for each cisenol tautomer in the region of vibrations of ketogroups and double bonds differ widely, which permits identification of the tautomers present in the mixture. The possible mechanisms of enolenol transformations of 3acyltetrinic acids are discussed.     

Change in the Absorption Spectra of Membranes Containing Co(III)‐ and Sn(IV) Tetraphenyl Porphyrins as a Result of the Use of Anion‐Selective Electrodes Based on Them

Electronic absorption spectra of the components of the membranes of anionselective electrodes containing Co(OH) and Sn(OH) Sn(OH)₂ tetraphenyl porphyrins (TPP) as electroactive substances and various softeners and lipophilic ionic additives have been investigated. 2Nitrophenyloctylic ether, bromonaphthalene, dibutyl phthalate, and dioctyl phthalate were used as softeners; tetradecyl ammonium nitrate and tetrakis(4chlorophenyl)potassium borate were used as ionic additives. To investigate the electronic absorption spectra, we dissolved the membranes in cyclohexane at different pH before and after their use. The influence of the acidity and the nature of a softener on the position and intensity of the absorption bands of metalloporphyrin in a membrane is discussed. It is shown that the use of membranes containing Co(OH)TPP in highly acidic media is accompanied by its demetallation and the formation of protonized forms of TPP. The membranes based on Sn(OH)₂TPP are more stable in acid media.     

Calculation of Out‐of‐Plane Vibrations of a Porphin Molecule

Using the DFT/B3LYP method with the base set 631G^**, we carried out calculation of the frequencies of the normal vibrations of porphin and of its five isotopic types. Scaling of force constants for outofplane vibrations has been performed in independent natural coordinates. The symmetry coordinates are introduced and a force field for outof plane vibrations of a porphin molecule in independent coordinates of symmetry is obtained. A new correlation of the frequencies of vibrations in the type of the symmetry B _1u for the isotopic type of the d ₂ porphin molecule is suggested on the basis of discrete analysis of the distribution of a potential energy.     

Manifestation of Extracoordination in the Resonance Raman Spectra of Water‐Soluble Cation Co‐Porphyrins

Resonance Raman spectra (RRS) of Co(II) and Co(III)5,10,15,20tetrakis(4Nmethylpyridinium)porphyrin ((Co^II(TmpyP4), and Co^III(TMPyP4)) in aqueous solutions at different pH as well as in organic solvents (methanol, ethanol, DMSO, DMF) are obtained. The increased sensitivity of the oscillation frequencies ₂, ₄, ₈, and ₆ — the markers of the oxidation state of a metal — to the nature of an axial ligand has been revealed. For Co^III(TmpyP4), the shifts of the indicated frequencies in extracoordination have turned out to be twofold larger than those for Co^II(TmpyP4). The spectral effects observed are related to different electron influence of the extraligands on the system of the porphyrin ring. In the case of Co(III)porphyrin, interaction of the d orbitals of the metal and the e _g ^*orbitals of the macrocycle is more efficient since its ionic radius is smaller than for the Co(II)complex. For Co^III(TmpyP4), a linear correlation between the oscillation frequencies ₂, ₄, ₈, and ₆ and the experimental Gutmann parameters characterizing the electronacceptor properties of solvents is found.     

Stability of an SHF Discharge Running in a Resonator‐Type Plasmatron on the Basis of a Waveguide‐Slit Applicator

Using the method of optical emission spectroscopy, the dynamics of the development and extinction of a pulsating SHF discharge, its time instability, and the ranges of stable pressurerelated operation of a resonatortype SHF plasmatron on the basis of an annular waveguideslit applicator were investigated. It is found that at the pressures of CF₄ and its mixtures with oxygen optimal for breakdown a virtually complete lack of reproducibility of the signals of the components of the emission spectrum (in particular, of the FI 703.7nm line) from pulse to pulse of the discharge has been established. A discharge in oxygen in the investigated range of pressures and powers is characterized by a good repetition of the form of the pulses of the emission spectrum line (considered in relation to the OI 844.6nm line).     

SYNFOS

An expression for the amplitude of a pulse of synchrotron radiation coherently scattered in the forward direction by a Mössbauer absorber consisting of randomly oriented paramagnetic ironcontaining molecules (for example, a frozen solution of a ⁵⁷Fe protein) in an applied magnetic field is derived from the theory of optics. It is assumed that the hyperfine splittings present in the Mössbauer nuclei can be described in the framework of the spinHamiltonian formalism. In the general case of a thick Mössbauer sample of this kind the response on an incident monochromatic and fully polarized beam cannot be given analytically because of the integrations involved. How nuclear forwardscattering for this general case is evaluated in the program package called SYNFOS is outlined.