Том 121, № 6 (2016)

Vibrational, rotational, and centrifugal spectroscopic constants; radiative parameters (the Einstein coefficients for spontaneous emission, the oscillator strengths for absorption, and the Franck–Condon factors), the r_v′v″-centroids; the wavenumbers of rotational lines of rovibronic transitions in the systems of bands A¹Σ⁺–X¹Σ⁺ of CsLi (0 ≤ v′ ≤ 25, 0 ≤ v″ ≤ 51, j = 0, 30, 50, 70, 100) and CsRb (0 ≤ v′ ≤ 30, 0 ≤ v″ ≤ 64, j = 0, 50, 100) molecules; and the radiative lifetimes for excited electronic states are calculated. The calculations are carried out on the basis of semiempirical potential curves constructed in this work. The calculated spectroscopic constants are compared with the experimental data. The lifetimes have been obtained for the first time.

Near-resonant Raman scattering from the electronic excited \({I_2}\left( {0_g^ + \left( {bb} \right)\xrightarrow{{hv}}D0_u^ + \to X0_g^ + } \right)\) state via the intermediate ion-pair D0_u⁺ state to the X one is observed for the first time. The Raman scattering follows a laser pulse. Its intensity I_R is inversely proportional to the squared value of detuning from the resonant D, 22, 51 ← 0_g⁺(bb), 7, 52 transition, (Δν₂)², according to the theory of near-resonant Raman scattering. The ratio of Raman D → X scattering intensity to that of the D0_u⁺, ν_D = 22, J_D = 51 → X0_g⁺ luminescence, I_R/I_D‒X < 1.5 × 10^–4 for Δν₂ > 0.5 cm^–1. The Raman and luminescence spectra are found to be identical.

Polarized Raman spectra of single crystals of lead diborate, PbB₄O₇ (PBO), are studied in detail at 300 K. The TO-, LO-, and IO-phonon lines of the A₁, A₂, B₁, and B₂ symmetries in the Raman spectra of this compound are assigned. Changes in the Raman spectra of the internal vibrations of boron–oxygen complexes upon transition from the crystalline to the glassy and the molten states of PBO are observed. On the basis of the obtained results, the regularities in the formation of boron–oxygen complexes in glasses, melts, and crystals of the PbO · 2B₂O₃, SrO · 2B₂O₃, and Li₂O · 2B₂O₃. diborate compositions are analyzed.

The effect of albumin on the photophysical properties of a photosensitizer of porphyrin nature, dimegin (disodium salt of 2,4-di(α-methoxyethyl)-deuteroporphyrin-IX), is studied. A slight decrease in the efficiency of generation of singlet oxygen and an increase in the luminescence intensity of the dimegin–albumin complex are shown.

Island nuclei formed on a polished quartz-glass surface upon heating to 1100°C have been investigated by confocal Raman spectroscopy. The structural and chemical composition of islands is shown to be a central nucleus, a shell around the nucleus, and a thin peripheral ring closing this shell. The formation and growth of individual regions of an island nucleus are found to occur in several stages. The shell around the nucleus is mainly formed by α-SiO₂ and α-cristobalite nanoparticles with a size ≥40 nm, whereas the α-SiO₂ nanoparticles in the nucleus and peripheral ring are 2–15 nm in size.

We have examined the Raman spectra of heavily doped lithium niobate single crystals (at close-to-threshold concentrations of doping cations): LiNbO₃:Zn (4.5 mol % ZnO), LiNbO₃:Mg (5.01 mol %):Fe (0.005 mol %), LiNbO₃:Mg (5.1 mol %), and LiNbO₃:Mg (5.3 mol % MgO). Low-intensity lines with frequencies at 209, 230, 298, 694, and 880 cm^–1 have been revealed for the first time. Analysis of the data from the literature on lattice dynamics calculations from first principles (ab initio) does not make it possible to unambiguously state that these lines correspond to fundamental vibrations of the А₂ symmetry species, which are forbidden for the С_3V⁶ (R3c) space group. At the same time, ab initio calculations unambiguously indicate that the experimentally observed low-intensity “superfluous” lines with the frequencies at 104 and 119 cm^–1 cannot correspond to vibrations of the А₂ symmetry species. It is most likely that they correspond to two-particle states of acoustic phonons with a total wave vector equal to zero.

Luminescence spectra of gradient-activated LiNbO₃:Yb, Er crystals with predefined concentration profiles of the optical centers are studied in different spectral regions. The process of electronic excitation energy transfer in the Yb³⁺–Er³⁺ system inside the LiNbO₃ matrix is calculated and dependences of the quantum efficiency of the up-conversion processes for the green and red luminescences of erbium ions on the time of excitation energy deactivation are obtained.

The fluorescence sensitization regularities have been investigated for oxazine dyes (Nile blue, cresyl violet (oxazine-9), and oxazine-170) in nanoparticles of complexes of 2-naphthoyltrifluoroacetone with trivalent ions of rare-earth metals. The fluorescence sensitization efficiencies of dyes in nanoparticles from the Sc(III), Eu(III), Sm(III), and Lu(III) complexes are compared. It is shown that the fluorescence sensitization efficiencies of dyes in nanoparticles from the Sc(III), Eu(III), and Sm(III) complexes has similar values and greatly exceed that for nanoparticles from the Lu(III) complexes. The quantum yields of sensitized fluorescence are determined for dyes in nanoparticles from the Sc(III), Eu(III), and Sm(III) complexes. The nanoparticles doped with oxazine-170 from Eu(III) complexes are found to have the strongest fluorescence.

A numerical solution has been obtained for a two-level atomic system interacting with a 101-component polychromatic field. The analytical method of recurrence relations has confirmed the numerical calculations. The resonance in the polarization spectrum follows the transition frequency.

Luminescence and photoconductivity of layered Cu₃In₅S₉ crystals at high levels of optical excitation are studied experimentally. A pulsed nanosecond Nd:YAG laser with built-in second and third harmonic generators to generate 1064-, 532-, and 355-nm radiation is used as a light source. It is found that the photoluminescence spectra exhibit two emission bands due to zone–acceptor level and impurity donor–impurity acceptor transitions. It is shown that the photoconductivity in Cu₃In₅S₉ is monopolar. The waveform of the photoconductivity consists of fast and slow components associated with two channels of recombination.

The quadratic Sagnac effect consists in a Michelson interferometer (MI) being located on a rotating base with a phase difference in its arms arising, the value of which depends on the orientation of the MI arms relative to the rotating base and on the angle of its rotation. This phase difference is caused by different values of the Newtonian (nonrelativistic) scalar gravitational potential of Coriolis forces acting on different MI arms, which leads to time dilation and varies with change in the angle of MI rotation. Distributions of the scalar gravitational potential of Coriolis forces over different parts of MI arms are considered. Allowance for this distribution makes it possible to calculate a value of the certain effect that is a higher approximation of the quadratic Sagnac effect. This effect is shown to be the Maraner effect known earlier, which also leads to a change in the phase difference of MI arms, but differs in value from the quadratic Sagnac effect. Consequently, the Maraner effect is a particular case of the quadratic Sagnac effect. Numerical estimations are performed.

Computer simulation is used to investigate a new regime of oscillation of fiber lasers in which passive mode-locking takes place simultaneously with the regime of regular undumped spiking induced by an intracavity saturable absorber. Such a superposition regime takes place when part of the output radiation of the laser operating in the regime of spiking is propagated through a fiber-optic delay line and is coupled back into the laser cavity in a time interval equal to the time interval between adjacent spikes. The advantages of the proposed regime of oscillation relative to other means of achieving passive mode-locking in fiber lasers are discussed. The proposed regime is of interest for obtaining reproducible high-energy light pulses.

The development and processing of three-dimensional images as a “hypercube” of spectral data in hyperspectral optical–electronic remote sensing systems are described in a formalized manner. The correlation identification of observed objects on the basis of spectral features is considered. The criterion for determining of similarity between vectors of recorded and reference spectral images of objects is based on their cross-correlation. Taking into the fact that the total spectral data array recorded by currently applicable hyperspectrometers is excessive for the solution of many issues related to remote sensing of the Earth, this paper proposes a method making it possible to reduce spectral data redundancy by selection of the most informative spectral channels. The essential dimension of the spectral data makes it possible to solve issues related to identification and classification of objects by spectral features through a limited number of very informative spectral channels selected in the areas where the function describing a spectral image of the observed object undergoes well-defined changes in behavior. The algorithm for selection of the most informative spectral channels, which is based on the determination of jump coordinates (major changes) of a spectral image, is substantiated. The selected channels meet the maximum likelihood criterion. The obtained experimental research data on object identification quality with involvement of real hyperspectral data of aerospace Earth remote sensing systems are reported. Five to twenty spectral readouts are needed to provide identification by a limited number of very informative spectral channels. This confirms the idea of existing essential dimensionality of the spectral data.