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.     

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.     

On the Effect of Increasing the Radiative-Transition Rate Near a Nanosize Point

A short review of theoretical and experimental studies concerning the photoexcited florescence and Raman scattering of light for a substance in a space containing small material bodies is presented. Calculations of the radiativetransition probability for atoms (molecules) in the vicinity of bodies with a size much smaller than the light wavelength are performed. The probabilities of the singlephoton and doublephoton transitions are shown to increase by factors of 9 and 81 in the vicinity of a nanosize sphere with dielectric constant ||\ 1. The probability of a radiative transition in the vicinity of the vertex of a conic needle bearing up against a plane (both with || 1) increases by factors of (/R _in)² and (/R _in)⁴ for singlephoton and doublephoton transitions, respectively (R _in is the curvature radius for the needle vertex). This theoretical result is suggested as an explanation of the effect of increasing the radiation process intensity in the experiments carried out in the studies cited below.     

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.     

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).     

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.     

Amplification Coefficient of the Anti‐Stokes Component of Raman Scattering

The theory of intracavity parametric interaction of the components of Raman scattering is developed in the prescribedintensity approximation, which takes into account the reverse reaction of the excited waves to the pumpingwave phase. It is shown that one can substantially improve the conversion efficiency or the amplification coefficient of the antiStokes component by selection of the intracavity geometry, the optimum phase relation between the interacting waves, the pumping level, and the phase mismatch.     

How to Determine the Amplitude-Phase Structure of a 2D Optical Field and a 2D Complex Transfer Function, with the Effect of the Medium Described by Convolution

We consider the solution to the phase problem in optics in application to registration and analysis of the amplitude–phase structure of twodimensional optical fields that form or transmit images, as well as the amplitude–phase structure of transfer and spread functions of media, in which light propagates, or those of systems that form fields or images. The idea of our method is to introduce two additional modulators that visualize phase information. We consider two variants of optical schemes designed for analyzing the amplitudephase characteristics of twodimensional optical fields as well as twodimensional complex transfer and spread functions. These schemes are special because the twodimensional structure of the fields is transmitted at a distance in a disturbing medium or system and four independent twodimensional intensity distributions are to be registered in the course of processing the twodimensional fields. To solve the problem, the first additional modulation preceding the transmitting medium is introduced in the scheme. Then the spectrum of spatial frequencies is formed by the optical system. The second additional spatial modulation is applied either in the optical system plane (the first variant of the scheme) or in the plane of spatial frequencies formed by the optical system (the second variant). A separate optical system is used for registration in the plane of spatial frequencies in the first variant of the scheme and in the image plane in the second variant. The intensity distributions obtained make it possible to solve the problem.     

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.     

A Cathodoluminescent Screen of Columnar Structure for Field Emission Displays

We have suggested and implemented a method of creation (growing) of sublimatescreens formed by singlecrystal luminophor columns which are perpendicular to an amorphous (e.g., glass) substrate. The diameters of the columns are 3–5 m, the height 7–10 m. The columnar singlecrystal structure of the screen ensures the high light yield and radiation color needed for field emission displays. It is possible to select the growing regime so that the columns are very closely spaced (1–2 m). The gaps can be filled with a conducting opaque material that increases the contrast of the screen and improves their electrical conductivity.     

Spectral‐Luminescence and Generation Properties of 1‐Aza‐2‐Methyl‐6‐Aminopyrene and of Its Protolytic Forms

Spectral manifestations of protolytic forms of 1aza2methyl6aminopyrene in ethanol and aqueous solutions are investigated. The ionization constants of the protolytic forms are determined. The generation properties and photostability of a neutral molecule and a cation in excitation by an excimer XeCl laser are studied.     

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.     

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.     

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.     

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.     

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.     

Quantum‐Chemical Investigation of Hydrogen Bonds in Porphin

Using the DFT Becke–Lee–Yang–Parr exchangecorrelation threeparametric functional (B3LYP), we have calculated the geometry, the electron density distribution, and the vibration frequencies for pyrrole, porphin, and their 13 analogs with a regularly varying structure. It is shown that the determining role in the change in the frequencies of stretching and outofplane deformation vibrations of porphin compared to pyrrole is played by intramolecular hydrogen bonds at the porphyrin macroring center. We have separately considered and compared with the data for porphin complexes of pyrrole with different intermolecular hydrogen bonds: with an aromatic ring (NH··· cluster formed by the pyrrole selfaggregation in the liquid state) and an unshared electron pair (NH···OH₂ and NH···NC₄H₄ clusters). The degree of participation of the NH group in the hydrogen bonds increases in the series NH··· cluster, porphin, NH···OH₂ and NH···NC₄H₄ clusters.     

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.     

Microwave Photonic Signal Down‐Conversion Using a Novel Two‐Frequency Bragg Grating Based Brillouin Fiber Laser

A simple technique using a novel twofrequency Bragg grating based Brillouin fiber laser to downconvert high frequency microwave photonic signals is presented. The mechanism of the Brillouin fiber laser and the principle of this technique for microwave photonic signal downconversion are analyzed. The 12GHz microwave photonic signals are experimentally downconverted to 1.13GHz IF signal with the technique.     

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.