Optics and Spectroscopy (v.122, #4)

A semiempirical calculation of the fine and Zeeman structure of 4p4f and 4p5f configurations of Ge I. Gyromagnetic ratios by G. P. Anisimova; Yu. I. Anisimov; A. P. Gorbenko; O. A. Dolmatova; I. R. Krylov; I. Ch. Mashek; G. A. Zygankova; M. Tchoffo (511-522).
The gyromagnetic ratios (g-factors) belong to the most important characteristics of atoms. For the 4p4f configuration of a germanium atom experimental values of g-factors are available only for four levels, while similar experimental data on the 4p5f configuration of Ge I are absent. Therefore, a theoretical study of the fine and Zeeman structures is topical for determining the gyromagnetic ratios. All the calculations are performed in the one-configuration approximation with the energy-operator matrix containing a maximum possible number of interactions, including magnetic: spin-orbit (own and other), spin-spin, and also orbitorbit interaction. The fine structure has been examined in three (LS, LK, and jK) approximations in order to establish the nature of coupling in the systems studied and the reliability of g-factors. Apart from the g-factors, in studying the Zeeman splitting, its specific features—the crossing and anticrossing fields of magnetic components— have been determined. A comparative analysis of g-factors was performed that showed that our results are in agreement with the available, albeit few in number, experimental data. At all stages, the corresponding energy-operator matrices were numerically diagonalized, i.e., all the results presented in the paper were obtained in the intermediate coupling scheme.

Comparative study of the structural and spectral properties of tetraaza- and tetraoxaannelated tetracirculenes by V. A. Minaeva; N. N. Karaush; B. F. Minaev; G. V. Baryshnikov; F. Chen; T. Tanaka; A. Osuka (523-540).
The IR spectrum of a recently synthesized tetraaza[8]circulene (4N) molecule has been investigated and completely interpreted based on the calculation of the molecular structure and force field within the density functional theory (DFT) using the B3LYP/6-311G(d,p) method. The calculation has also successfully explained the X-ray diffraction data. The same method has been used to calculate the tetraoxa[8]circulene () molecule and perform a comparative analysis of the IR spectra of both molecules. In contrast to , the 4N molecule exhibits strong fluorescence, which hinders measurement of its Raman spectrum; hence, it is only predicted based on the DFT calculation in this study. A comparison of the IR and Raman spectra of the 4N molecule with the experimental and theoretical analogs for the molecule has made it possible to assign all the observed vibrational transitions and explain the nature of normal vibrations in these complex molecules.

The effect of a double structure of saturated absorption resonance in the field of counterpropagating light waves interacting with an atomic gas is studied. The experimental observation of this effect was first reported in 2011 in a work by our colleagues at the P.N. Lebedev Physical Institute of the Russian Academy of Sciences (Laboratory of Frequency Standards). The essence of the effect lies in the fact that, on exciting an open dipole transition, another, narrower, resonance of an opposite sign can be observed at the center of the ordinary saturated absorption resonance. A theoretical analysis of this effect has also been performed in this work in terms of a simple spectroscopic model of an atom with two nondegenerate energy levels without taking into account higher spatial harmonics of atomic polarization and polarizations of light waves (scalar model). The present work is devoted to the development of a theory of the formation of a central narrow resonance for the example of a real F g = 1 → F e = 1 atomic transition and to the study of its main characteristics (amplitude, width, contrast, and amplitude-to-width ratio). In addition, the theoretical results obtained without taking into account the influence of higher spatial harmonics and with inclusion of the influence of first higher harmonics are compared. This comparison shows that their influence on the parameters of the new nonlinear resonance is strong even in moderately intense light fields (R ~ γ, where R is the Rabi frequency). The results of this study can be of interest for quantum metrology, as well as for many experiments in which the laser-radiation frequency is stabilized by the saturated absorption resonance on open dipole transitions in atoms and molecules.

Isotopic shifts of the 3s[3/2] 1 0 –2р 6(1 S 0) and 3s'–2р 6(1 S 0) transitions, equal, respectively, to 417 ± 20 and–98 ± 20 MHz, have been measured using the 0.63-μm radiation of a helium–neon laser and opto-magnetic resonances induced by the interference of the reactive components of fields in overlapping areas of the emissions of isotopic atoms. Combining these results with the absolute specific mass shift of the 3p[5/2]2 level (–647 MHz), the isotopic mass shift of the ground state of neon equal to 3223 ± 30 MHz, and its specific mass shift equal to–9782 ± 30 MHz have been determined.

A theory of the transient absorption of femtosecond light pulses at a two-photon–one-photon double resonance on adjacent interband transitions in the electronic system has been developed. Approximate expressions for the reactive component of the nonlinear polarization of the three-level system, P s, which determines the absorbed power in the medium, have been obtained, and the dependences of P s on the light intensity and detunings of resonances have been calculated.

The dependences of the energy that is absorbed in a crystal exposed to the action of a femtosecond light pulse on the radiation intensity at a fixed pulse duration and on the pulse duration at a fixed pulse energy have been determined under the conditions of a two-photon–one-photon double resonance on interband transitions in the crystal.

Electronic structure and optical spectroscopy of the GdRhGe compound by A. V. Lukoyanov; Yu. V. Knyazev; Yu. I. Kuz’min; S. Gupta; K. G. Suresh (574-579).
The optical properties of the GdRhGe compound have been investigated in a wide spectral range by ellipsometry. Self-consistent calculations of the electronic structure have been performed within the local electron spin density approximation with a correction to strong electron interactions in the 4f shell of gadolinium ions (LSDA+U method). The experimental dispersion relation of the optical conductivity in the region of interband light absorption is interpreted based on the results of calculating the electron densities of states.

Spectroscopy of optical centers of Eu3+ ions in partially stabilized and stabilized zirconium crystals by M. A. Borik; T. V. Volkova; E. E. Lomonova; V. A. Myzina; P. A. Ryabochkina; N. Yu. Tabachkova; A. N. Chabushkin (580-587).
The structure of the optical centers of Eu3+ ions in tetragonal (ZrO2)1–xy (Y2O3) x (Eu2O3) y (х = 2.7–3.6; y = 0.1) and cubic (ZrO2)1–xy (Y2O3) x (Eu2O3) y (х = 8–38; y = 0.1–0.5) crystals of solid solutions on the basis of zirconium dioxide is studied using the methods of optical and Raman-scattering spectroscopy. Characteristic optical centers of Eu3+ ions with different crystalline environments are revealed in the above compounds.

The influence of synthesis conditions on the stability of tris(8-hydroxyquinoline) aluminum organometallic luminophore by A. A. Akkuzina; A. V. Khomyakov; R. I. Avetisov; I. Ch. Avetissov (588-590).
Single-phase crystalline luminophore tris(8-hydroxyquinoline) aluminum (Alq3) has been synthesized at Т = 483 K and a partial pressure of 8-hydroxyquinoline vapor from 0.15 to 6.12 Torr. The influence of P 8-Hq on the luminescent characteristics of crystalline Alq3 samples has been studied. It has been found that an increase in P 8-Hq led to a shift of the photoluminescence-band maximum and to a change in the photoluminescence-decay kinetics. It has been shown that Alq3 synthesized at Т = 483 K and P 8-Hq = 6.12 Torr had the most stable spectral-luminescent characteristics. The results obtained are discussed taking into account defect formation in crystalline Alq3.

Spectral-luminescent characteristics of fluorophosphate glasses with zinc sulfide nanocrystals by Zh. O. Lipatova; E. V. Kolobkova; A. O. Trofimov; N. V. Nikonorov (591-595).
Fluorophosphate glasses doped with ZnS are studied. The properties of ZnS nanocrystals formed are determined using X-ray-diffraction analysis and optical spectroscopy. The size and the band-gap width of these crystals are determined by the Tauc method. It is shown that ZnS nanocrystals luminesce in the visible spectral region with a low (2–3%) absolute quantum yield.

Quantum yield and rate constant of the singlet 1Δ g oxygen luminescence in an aqueous medium in the presence of nanoscale inhomogeneities by E. S. Jarnikova; M. V. Parkhats; A. S. Stasheuski; S. V. Lepeshkevich; B. M. Dzhagarov (596-601).
The quantum yields and lifetimes of photosensitized luminescence of the 1Δ g state of singlet oxygen in an aquatic media with a controlled concentration of dielectric anisotropy centers (polyethylene glycol) have been measured using the methods of laser fluorometry. It is established that the quantum yield and the rate constant (k r ) of the a 1Δ g X 3Σ g - luminescence of 1O2 increase as the polymer concentration increases. The effect is analyzed within a general approach involving a relationship between kr and dielectric properties of the medium and is explained by the increased density of photon states and the local field factor in the space around O2(а 1Δ g ).

Polarized fluorescence in NADH under two-photon excitation with femtosecond laser pulses by O. S. Vasyutinskii; A. G. Smolin; C. Oswald; K. H. Gericke (602-606).
Polarized fluorescence decay in NADH molecules in aqueous solution under two-photon excitation by femtosecond laser pulses has been studied. The excitation was carried out by linear and circularly polarized radiation at four wavelengths: 720, 730, 740, and 750 nm. Time-dependent polarized fluorescence signals were recorded as a function of the excitation light polarization and used for determination of a set of molecular parameters, two lifetimes characterizing the molecular excited states, and the rotation correlation time τrot. The results obtained can be used to create and prove theoretical models describing the intensity and polarization of fluorescence in NADH involved in the regulation of the redox reactions in cells and tissues of living organisms.

Raman spectroscopy of the interface between a thin nanostructured ZnO film and fullerene C60 by E. A. Zakhidov; M. A. Zakhidova; A. M. Kokhkharov; Sh. K. Nematov; R. A. Nusretov; V. O. Kuvondikov; A. A. Saparbaev (607-614).
The resonance and nonresonance Raman scattering in the interface between a thin ZnO film with a well-developed nanostructured surface morphology and a layer of fullerene C60 molecules deposited on this film has been investigated. It is shown that the intensity of the interaction between the C60 molecules and ZnO film surface can be estimated based on the spectral scattering characteristics.

We have analyzed the parameters of the Franck–Condon and Herzberg–Teller interactions, which form the fine-structure spectra of diphenylbutadiene substituted derivatives with the general formula X–Ph–(C=C)2–Ph–Y (where X, Y = H, NO2, N(CH3)2, and NH2 are the substituents in different combinations) in solutions of n-paraffins at 4.2 K. The influence of substituents on the vibronic parameters of characteristic bands that describe the states (vibrations, types of deformations upon excitation) of the phenyl rings and diphenylbutadiene polyene bridge has been considered. Data on the influence of the H, NO2, N(CH3)2, or NH2 terminal fragment on the parameters of the intra- and intermolecular interactions of diphenylbutadiene substituted derivatives have been presented.

The influence of perchloric acid on the spectral-luminescent characteristics of coumarin-7 and coumarin-30 in acetonitrile and ethanol is studied. A probable mechanism and methods of controlling the protonation of nitrogen atoms of the phenylimidazole fragment are discussed.

The third-order nonlinear optical properties in polymer ferroelectrics by K. A. Verkhovskaya; A. D. Grishina; T. V. Krivenko; V. V. Savel’ev; A. S. Laryushkin; A. V. Vannikov (628-631).
The third-order susceptibility of vinylidene fluoride-trifluoroethylene (VDF-TrFE) copolymer are analyzed by using the z-scan technique with a nanosecond laser as an excitation source. It is established that optical transmittance of the VDF-TrFE samples decreases after their polarization in an electric field.

Fluorescent spectral studies of the toxic effect of chlororganic pesticides on the biochemical parameters of synaptosomes by K. M. Giraev; K. S. Bekshokov; N. A. Ashurbekov; N. M. Abdullaeva; E. Kh. Israpov; I. Sh. Gashimov (632-640).
The results of the study of the fluorescence spectra of suspensions of synaptosomes, which have been exposed to a chlororganic pesticide, thiamethoxam, at a concentration of 50 MPC during different time periods, at the excitation/emission wavelengths of 290 ± 5/310–600, 340 ± 5/360–700, and 420 ± 5/450–800 nm are given for the first time. It has been demonstrated that the development of intoxication results in weakening of the fluorescence intensity of tryptophan, NAD(P)·H, derivatives of vitamin B6, and vitamin А and in an increase in the fluorescence of pyridoxic acid, lipofuscin, and flavin and porphyrin complexes. The results of the spectral studies indicate that the toxic effect of the chlororganic pesticide for the functioning of living systems is based on free radical toxicity.

Three-dimensional dissipative quasi-solitons in carbon nanotubes by N. N. Konobeeva; M. B. Belonenko (641-645).
The propagation of three-dimensional quasi-solitons in a system of carbon nanotubes with two-level impurities has been investigated. The system of effective equations is derived in the form of analogs of the Sine–Gordon classical equation and Bloch equations. The effects observed with a change in the inverse population and damping parameter have been studied.

The theoretical and experimental investigations of photonic band gaps in one-dimensional photonic crystals created by micromatchining silicon, which have been performed by the author as part of his doctoral dissertation, are presented. The most important result of the work is the development of a method of modeling photonic crystals based on photonic band gap maps plotted in structure–property coordinates, which can be used with any optical materials and in any region of electromagnetic radiation, and also for nonperiodic structures. This method made it possible to realize the targeted control of the optical contrast of photonic crystals and to predict the optical properties of optical heterostructures and three-component and composite photonic crystals. The theoretical findings were experimentally implemented using methods of micromatchining silicon, which can be incorporated into modern technological lines for the production of microchips. In the IR spectra of a designed and a fabricated optical heterostructure (a composite photonic crystal), extended bands with high reflectivities were obtained. In a Si-based three-component photonic crystal, broad transmission bands and photonic band gaps in the middle IR region have been predicted and experimentally demonstrated for the first time. Si–liquid crystal periodic structures with electric-field tunable photonic band-gap edges have been investigated. The one-dimensional photonic crystals developed based on micromatchining silicon can serve as a basis for creating components of optical processors, as well as highly sensitive chemical and biological sensors in a wide region of the IR spectrum (from 1 to 20 μm) for lab-on-a-chip applications.

The propagation of an electromagnetic wave through a layer of a uniaxial anisotropic metamaterial with the components of its permittivity tensor close to zero and the reflection of the wave from the layer have been considered. The occurrence of transmission maxima of the electromagnetic wave at specific angles of incidence has been confirmed. It has been shown that, when studying this effect, one cannot neglect the absorption, because this neglecting leads to unrealistic predictions, such as a total transmission of the wave by the layer of the anisotropic metamaterial at special angles of incidence of the wave.

On the emission of radiation by an isolated vibrating metallic mirror by M. V. Arkhipov; I. Babushkin; N. S. Pul’kin; R. M. Arkhipov; N. N. Rosanov (670-674).
Quantum electrodynamics predicts the appearance of radiation in an empty cavity in which one of the mirrors is vibrating. It also predicts the appearance of radiation from an isolated vibrating mirror. Such effects can be described within the framework of classical electrodynamics. We present the qualitative explanation of the effect, along with the results of numerical simulation of the emission of radiation by an isolated vibrating metallic mirror, which can be induced by mirror illumination by an ultrashort pulse of light. The dynamics of conduction electrons in the metallic mirror is described by the classical Drude model. Simulation was performed for the cases of mirror illumination by either a bipolar or a unipolar pulse.

Examination of the temperature influence on the acousto-optic filters performance by S. N. Mantsevich; T. V. Yukhnevich; V. B. Voloshinov (675-681).
Acousto-optic (AO) interaction is widely used in devices for analysis and control of optical radiation. Acousto-optic devices are mainly used for crystalline media possessing strong anisotropy. The properties of such materials may exhibit significant changes under the influence of temperature conditions affecting the device characteristics. This study considers the influence of temperature on the performance of wide-aperture AO filters based on KDP and TeO2 crystals.

The conditions for obtaining 20% efficiency of a single-wavelength mode-locked carbon monoxide (CO) laser for intracavity irradiation of a substance with a small cross-section photon absorption of ~5 × 10‒22 cm2 have been considered, and the possibility of a long working lifespan of this single-wavelength CO laser has been justified. A laser-output power of 1 kW has been found sufficient for intracavity irradiation despite the small absorption cross section. The calculated efficiencies of this mode-locked laser generating a single line at ~5.3 μm and a number of lines in the 5.0–5.6 μm region are compared with the efficiency of an experimental CO laser.