Optics and Spectroscopy (v.114, #1)

The relative intensities of the M 5 N and M 4 N satellites of Pb under electron bombardment of thick targets in the range of accelerating voltages U = 5−30 kV are experimentally investigated. Based on the previously proposed model of M X-ray emission, the relative intensities of these satellites are calculated using the total ionization cross sections of M subshells under electron impact found in different approximations. It is established that, among the models yielding analytical expressions for calculating total ionization cross sections, the model of classical binary collisions provides the best agreement with experimental data in the electron energy range under study. The parameters of the semiempirical Bethe formula for calculating the ionization cross sections of Pb M subshells under electron impact are determined.

We present optical emission characteristics of the titanium plasma produced by the fundamental (1064 nm) and second (532 nm) harmonics of a Q-switched Nd: YAG laser using laser induced breakdown spectroscopy (LIBS). The experimentally observed line profiles of neutral titanium (Ti I) have been used to extract the electron temperature (T e ) using the Boltzmann plot method. The electron number density (N e ) is calculated using the Stark broadening profile of 368.73 nm spectral line. Beside we have studied the spatial variation of electron temperature and number density as a function of laser energy for titanium plasma by placing the target material in air (at atmospheric pressure). We have determined the electron temperature and the electron number density along the axial position of the plasma plume.

Broadening coefficients γ and interference coefficients ξ are calculated for different bands of the ammonia molecule in the case of line broadening by the pressure of argon and helium. A model intermolecular potential is used. It is shown that taking into account the interference effect changes the calculated values of γ, which suggests that the model potential parameters should be redetermined. The vibrational dependence of coefficients ξ is analyzed, and they are compared to coefficients ξ calculated for the same lines of the ammonia molecule pressure broadened by H2, O2, N2, and NH3.

Emission characteristics of a barrier discharge in an Ar-H2O mixture by A. A. General; V. A. Kel’man; Yu. V. Zhmenyak; Yu. O. Shpenik; M. S. Klenovskii (25-29).
We have experimentally studied the UV radiation of a low-temperature barrier discharge plasma in an Ar-H2O mixture. The spectral interval 300–400 nm has been examined in detail. Addition of argon with a pressure of 24 kPa to a barrier discharge in water vapor at a pressure of ∼0.1 kPa leads to a ninefold increase in the UV radiation power of excited hydroxyl molecules. An increase in the duration of the UV radiation pulse of the mixture in the longitudinal discharge decay has been achieved for the first time, which may be direct evidence of energy transfer from metastable argon atoms to water molecules. An estimate of the upper boundary of the dissociative excitation rate constant of hydroxyl molecules OH*(A 2Σ+) upon interaction of metastable argon atoms with water molecules has been obtained.

Quantum-chemical investigation of the structure and electronic absorption spectra of electroluminescent zinc complexes by B. F. Minaev; G. V. Baryshnikov; A. A. Korop; V. A. Minaeva; M. G. Kaplunov (30-40).
Using the quantum chemical methods of the density functional theory and of the electron density topological analysis, we have studied the structure of two recently synthesized electroluminescent zinc complexes, one with aminoquinoline ligands and the other with a Schiff base (N,O-donor). The energies and intensities of vertical excitations for the molecules under study have been calculated in terms of the PM3 semiempirical approximation taking into account the configurational interaction between singly excited singlet excited states. Good agreement between calculation results and experimental data on the electron density topological characteristics and on the visible and UV absorption spectra has been obtained.

Separation of closely located IR Fourier absorption bands using the genetic algorithm by D. I. Kamalova; D. Z. Galimullin; M. E. Sibgatullin; E. R. Shaimukhametova; M. Kh. Salakhov (41-46).
The genetic algorithm was used for analyzing experimental closely located analytical conformation-sensitive IR Fourier absorption bands of low-molecular compounds incorporated into a polymeric matrix. Model experiments demonstrated the efficiency of spectrum reconstruction using the genetic algorithm as compared to the least squares method in the case of closely located components and in the presence of low-frequency noise in the spectrum.

Excitation of adenine molecules by slow electrons by N. M. Erdevdi; V. V. Zvenigorodskii; O. B. Shpenik; L. G. Romanova (47-51).
The excitation of adenine molecules in the gas phase by slow electrons is studied by optical spectroscopy. The emission spectra of the molecule in the region of 250–500 nm upon excitation by slow electrons in the energy range of 15–120 eV, as well as the optical excitation functions of the most intense emission bands, are presented.

Diffraction of atomic wave packets from a standing laser wave with a Gaussian profile is studied theoretically and numerically in pursuing the aim of creating high-resolution spatial structures in optical nanolithography. To this end, we propose to use nonadiabatic transitions between two optical potentials which take place when square of the value of detuning off the resonance is approximately equal to the Doppler shift. In this case, atomic wave packets experience splitting at nodes of the standing wave, which allows creating atomic structures on a substrate with a period substantially smaller than the standard nanofabrication limit equal to half the wavelength of light. We propose a scheme of the experiment for the observation of nonadiabatic transitions and splitting of the wave of matter caused by them. A number of computer simulations with parameters corresponding to real atoms have been performed, which exhibit this effect in both momentum and coordinate spaces.

We have analyzed the intensity distributions in fine-structure fluorescence and fluorescence excitation spectra of trans-stilbene in n-hexane at 4.2 K. Modeling the spectra by representing each of the vibronic transitions by a zero-phonon line and a phonon wing with certain parameters (widths, Debye-Waller factors) made it possible to determine relative intensities of vibronic transitions. The parameters of Franck-Condon and Herzberg-Teller interactions, which form the fine-structure spectra of stilbene, have been calculated and compared with previously obtained parameters of intramolecular interactions in 1,4-distyrylbenzene.

The spectral and luminescent properties of film composites based on photoconductive poly-N-epoxipropylcarbazole and nonphotoconductive polyvinylbutyral with admixtures of cationic and anionic polymethine dyes, as well as the effect of an external magnetic field on these properties, are studied. It is found that the magnetic field affects the intensity and kinetics of the delayed fluorescence and recombination luminescence of the cationic dye in photoconductive films. This is explained by specific features of photogeneration of charge pairs, namely, by the participation of the singlet and triplet excited states of dye molecules in this process, as well as by the singlet-triplet conversion in dye molecules and photogenerated charge pairs.

The results of synthesis of new Pt(II) complexes with N,N′-ethylene-bis(3-methoxysalicylideneiminate) and N,N′-2,3-dimethylbutane-2,3-diyl-bis(3-methoxysalicylideneiminate) ligands and their investigation by X-ray photoelectron spectroscopy and UV-visible absorption and emission spectroscopy are discussed. The degradation channels of excited electronic states of the complexes are determined.

Spectral investigation of photochemical properties of polypropylene microfiber by O. N. Chaikovskaya; A. Yu. Petrova; T. D. Malinovskaya; V. R. Artyushin (78-82).
Using the fluorescence, IR, and electronic spectroscopy methods, we have investigated the spectral characteristics of the surface of a polypropylene microfiber before and after their UV irradiation. We have studied the degradation of naphthalene and phenol in water exposed to UV radiation in the presence of fibers. As a radiation source, we used a KrCl excilamp with a radiation wavelength of 222 nm. It has been revealed that, after irradiation, photooxidation of the fiber surface occurs. The degree of crystallinity of examined samples remains almost the same after their irradiation. We show that, as a result of the adsorption of naphthalene and phenol on the fiber surface, their concentration in aqueous solutions efficiently decreases. Maximally, the concentration of naphthalene decreased 21-fold and that of phenol decreased 4-fold. Under UV irradiation of the system toxicant + water + fiber by the KrCl excilamp, fluorescent photoproducts are formed in the system and are adsorbed on the fiber surface.

Optical absorption and electronic structure of intermetallic compound RuIn3 by Yu. V. Knyazev; Yu. I. Kuz’min; I. A. Nekrasov (83-86).
The optical properties of intermetallide RuIn3 are investigated by ellipsometry in the spectral range of 0.22–10 μm. The experimental data point to the existence of an energy gap of about 0.5 eV in the electronic spectrum of the compound. The density of the electron states and interband optical conductivity are calculated in terms of the density functional theory. The experimental and theoretical spectra of the optical conductivity are compared. It is found that the formation of basic absorption bands is caused by interband transitions of electrons of the d-band of Ru and p-band of In.

Luminescence kinetics of two-component molecular systems in porous glasses by Yu. V. Starokurov; S. N. Letuta; S. N. Pashkevich; T. V. Antropova; Yu. A. Gordeeva; A. M. Saletsky (87-90).
The kinetics of bimolecular photoreactions accompanied by a characteristic delayed emission of reactant molecules is studied in nanoporous silica glasses upon selective activation of a two-component luminophore system (erythrosine-anthracene) by a short (10 ns) pulse of a Nd3+:YAG laser (532 nm). Time-resolved luminescence signals with different shapes are recorded in different spectral regions. The emission at a wavelength of 430 nm is identified as the sensitized delayed annihilation fluorescence of anthracene. The long-time luminescence in the region of 570 nm consists of thermally induced delayed fluorescence of erythrosine and an emission resulting from heterogeneous annihilation of triplet excitations of erythrosine and anthracene. The effect of pore sizes on the triplet-triplet energy transfer efficiency is determined.

The fundamental vibrations of the (PO3) 4 anions in the AgGd(PO3)4 crystal are predicted by employing the correlation method based on the group theory. Nine external vibrations are allowed with no coincidence activity between infrared and Raman spectra. The free PO3 ion with C 3v molecular symmetry has six normal vibrations. Due to the crystal-field splitting effect, the six normal modes of vibrations are split into 96 intramolecular vibrations. Symmetric and asymmetric stretching and bending modes are identified with determining of their spectral activity.

Optical echo holography by E. I. Shtyrkov (96-103).
The basic physics and applications of an unconventional area in holography that is based on the interference of light-induced atomic coherent superposition states in a resonant medium are discussed.

Properties of evanescent waves in polarized media in a constant external electric field: I. The compensated antiferromagnetic by D. V. Kulagin; G. G. Levchenko; A. S. Savchenko; A. S. Tarasenko; S. V. Tarasenko; V. G. Shavrov (104-111).
The dependence of formation and propagation conditions for evanescent waves of the TM and TE types on the magnitude and direction of a constant external electromagnetic field is studied by an example of the two-sublattice model of a centrally symmetric antiferromagnetic in the collinear phase.

Components of the Stokes vector are shown to undergo amplitude- and phase-frequency variations for a magneto-optical thin rod-shaped crystal located under conditions of magnetomechanical resonance when the variable magnetic field is directed at an acute angle to the light propagation axis coinciding with the crystal oscillation axis. It is noted that the phase relations for these components must be taken into account for polarized light when finding the connection between the variable and constant components of the Stokes vector.

Visualization of type II fiber Bragg gratings induced in a birefringent fiber with an elliptical stress cladding by S. V. Varzhel’; V. V. Zakharov; G. N. Vinogradova; A. V. Veniaminov; V. E. Strigalev (116-119).
Experimental results on visualization of type II fiber Bragg gratings induced in a birefringent fiber with an elliptical stress cladding are presented. The gratings are recorded by a single pulse of an excimer KrF-laser by means of the phase-mask method. Images of the gratings are obtained in a bright field using contrasting techniques such as differential interference contrast and dark field. It is shown that single-pulse recording forms several type II Bragg gratings in the optical fiber. The spatial profile of these gratings corresponds to the phase mask period. Microcracks due to which type II gratings are induced are localized both on the boundaries between the fiber core and claddings surrounding it and at some distance from them.

We have considered the electrostatic problem for a two-layer nonconfocal spheroid. The approach is based on surface integral equations that are similar to equations in terms of the extended boundary condition method for wave problems. Electrostatic fields are related to scalar potentials, which are represented as expansions in terms of eigenfunctions of the Laplace equation in two spheroidal coordinate systems, while unknown expansion coefficients are determined from infinite systems of linear algebraic equations. The constructed rigorous solution to the problem coincides with the known solution in a particular case of a confocal two-layer spheroid. In addition, for the nonconfocal two-layer spheroid, we have constructed an explicit approximated solution assuming that the field in the particle core is constant. This solution coincides with the rigorous solution if the scatterer shells are confocal. The formula found for the polarizability of the two-layer nonconfocal spheroid has a very simple form compared to the previously proposed cumbersome algorithm (B. Posselt et al., Measur. Sci. Technol. 13, 256 (2002)) and is more efficient numerically.

Numerical experiments are outlined to verify if ratios of the nonlinear surface susceptibility tensor components, that govern second harmonic optical effects in centrosymmetric media, can be unambiguously determined by ellipsometry, using a recently proposed technique. The corresponding theoretical model considers only the effects associated with a single, nonmagnetic interface (between two centrosymmetric media) assumed to be an ideal surface, whose crystallographic point group is either 4mm, 6mm or ∞ m The objective has been to explore how both random and systematic errors in the experimental data related to the state of polarization of the second harmonic radiation influence complex values of the ratios in this case. A procedure used for fitting the sample data is shown to deliver unambiguous results for the unknown ratios thus confirming the applicability and usefulness of the technique.

The influence of filtration in the Fourier holography scheme, which is caused by nonlinearity of the exposure characteristics of recording media on the homogeneity of processed images in the first two statistical moments, has been investigated. Formulas approximating the dependences of the estimates on the generalized rate (ratio of image size to correlation length) are proposed. The influence of filtration on the change in the dependence of estimated homogeneity on the generalized rate is shown, and the influence of random phase spectrum on the variance of estimates is determined. It is shown that the two practical methods used to provide the desired generalized rate-change in the image size and filtration-differently affect the estimates.

Stimulated Mandelstam-Brillouin scattering at small angles is considered in the case of a powerful laser beam propagating in the static mode in an unbounded medium. In contrast to the pulse mode, a hypersonic wave can be formed not only in the backward direction, but also in the forward direction at small angles. In this work, the latter case is considered as having the smallest value of the threshold intensity. It is shown that finite dimensions of the beam significantly change the excitation conditions for a scattered radiation owing to the mismatch of the wave triplet due to diffraction effects. Determination of the threshold intensity is shown to be possible using the well-known expressions for a plane wave only if the Fresnel number of the beam on the path the length of which is equal to the distance of the optical wave decay due to absorption in the medium is much larger than unity. Moreover, a large number of decay distances of the hypersonic wave must fall on the beam radius. When these conditions are not satisfied, the threshold intensity increases as compared to the plane wave.

All-solid-state doubly resonant intracavity frequency sum mixing orange yellow laser with 3.2 W output power at 593.5 nm by P. F. Zhu; B. Li; W. Q. Liu; T. H. Liu; C. X. Fang; Y. Zhano; Y. Yao; Q. Zheng (151-155).
A compact and efficient 593.5 nm orange-yellow laser is realized using doubly resonant intracavity sum frequency mixing. Two Nd: YVO4 crystals are employed as the gain crystals. In two sub-cavities, 1064 nm radiation from one Nd: YVO4 and 1342 nm radiation from the other Nd: YVO4 are mixed to generate 593.5 nm orange-yellow laser. In the overlapping of the two cavities, sum frequency mixing is achieved in a type I critical phase matching (CPM) LBO crystal. An output power of 3.2 W at the wavelength of 593.5 nm is obtained with total incident pump power of 38 W. The optical to optical conversion efficiency is up to 8.4% and the stability of the output power is better than 2.48% in 8 h. To the best knowledge, this it the highest watt-level laser at 593.5 nm generated by diode end pump all-solid-state technology.

The wave equation for the electromagnetic field that propagates in carbon nanotubes with allowance for the proper nonlinearity of the medium is analyzed. An effective equation having the form of an analog of the classical sine-Gordon equation is obtained and analyzed numerically. The dependence of the pulse on the nonlinearity constant of the medium is revealed. The evolution of the electromagnetic pulse is studied.