


Том 127, № 2 (2019)
- Год: 2019
- Статей: 27
- URL: https://ogarev-online.ru/0030-400X/issue/view/10111
Spectroscopy and Physics of Atoms and Molecules
Inversion of the Contribution of an Isotope of Small Relative Concentration to Total Absorption Coefficient of a Mixture of Neon Isotopes Associated with the 3s2–2p4 Transition
Аннотация
Absorption of probe laser radiation by a mixture of even isotopes of neon in a gas discharge plasma is investigated by the method of magnetic scanning of 3s2–2p4 transition. The contours of absorption lines of isotopes are resolved by means of numerical modeling. It is discovered that, upon decrease in relative concentration of one of the isotopes, its contribution to absorption is replaced by gain. The effect is found to be caused by radiative transfer of excitation energy between atoms of different kinds in the absence of a difference in level energies (the process known as optical pumping). The effect of this mechanism turned out to be substantial for the upper level transitions from which to the ground state are allowed while being absent for the lower level of the transition from which such transitions are forbidden although other decay channels are available.



The Energy Spectrum and Optical Properties of Fullerene С36 within the Hubbard Model
Аннотация
The anticommutator Green’s functions and the energy spectra of fullerene С36 and endohedral fullerene La@C36, with both of them belonging to the D6h symmetry group, are obtained analytically within the Hubbard model in the mean-field approximation. Using group-theory methods, their energy states are classified and allowed transitions in the energy spectra of the С36 and La@C36 molecules, both belonging to the D6h symmetry group, are determined.



\({{{v}}_{2}}\)-Dependences of the Rotational Contributions to the Effective Dipole Moment of the H2O Molecule and Their Effect on the Broadening and Shift of Lines Induced by the Pressure of Buffer Gases
Аннотация
The dependences of the rotational contributions to the effective dipole moment of the H2O molecule on vibrational quantum number \({{{v}}_{2}}\), which corresponds to the large-amplitude bending vibration of the molecule, have been determined numerically. Different representations for the dipole moment surface of the H2O molecule and different potential functions that determine the set of vibrational states E(\({{{v}}_{2}}\)) have been used in calculations. The effect of the calculated contributions on the broadening and shift of H2O lines induced by the pressure of argon, krypton, hydrogen, and helium has been analyzed. It has been shown that this effect is significant for the shift of rotational lines and for the shift of lines from the vibrational bands for which the difference between the values of rotational quantum number Ka from the upper and lower states of the transition is greater than or equal to 3.



The Fine Structure of Alkali Metal Atoms in Inelastic Collisions with Hydrogen
Аннотация
A method is proposed for calculating the rate constants of inelastic processes occurring during collisions of alkali metal atoms and their positive ions with hydrogen atoms and negative ions, taking into account the sublevels of the fine structure of alkali metal levels. The results of the application of the proposed method are presented in this paper based on the example of the KH and RbH collisional systems.



A “Dipole–Induced Dipole” Quantum Model and the Effect of an Inert Environment on the Intensity of Infrared Absorption
Аннотация
A theory of the imaginary part of isotropic polarizability induced by dipole–dipole interactions between isotropically polarizable particles has been developed on the basis of diagram technique. A classification of single infrared resonances corresponding to the cases of allowed absorption and absorption induced by intermolecular interactions has been proposed. A summation of the diagram contributions describing the change in the intensity of the allowed absorption due to the effect of the reaction field of the environment has been carried out for the dipole–induced dipole (DID) scheme. The strict results obtained in such a way contradict the Onsager–Bettcher model, which is semiempirical. The numerical estimates show that the role of the reaction field in the observed changes in the intensity of the vibrational bands of the simplest model systems (HCl and HBr in inert solvents) is small and decreases with increasing solvent particle size, which indicates the inadequacy of the DID and Onsager–Bettcher models to the experimental data.



Calculation of Vibrational Parameters of an Electride-Like Molecule Li4C4H2N2 and the Pyridazine Molecule C4H4N2
Аннотация
The frequencies and intensities are calculated for fundamental transitions between vibrational states of an electride-like molecule Li4C4H2N2 that can be obtained from the pyridazine molecule C4H4N2 by replacing two hydrogen atoms by lithium atoms and adding two other lithium atoms to nitrogen atoms. Spectral parameters of Li4C4H2N2 are calculated in the harmonic and anharmonic approximations using the MP2, CCSD, and QCISD methods with the sets of atomic functions aug-cc-pVDZ and aug-cc-pVTZ. For comparison the absorption spectrum of a pyridazine molecule was calculated in the same approximations. The calculations showed that, upon introducing lithium atoms into the pyridazine molecule, new intense bands appear and the spectral parameters of the bands present in the pyridazine spectrum are significantly changed. The results obtained may be useful for spectroscopic observation and identification of the new c-ompound.



Spectroscopy of Condensed States
Angular Dependences of the Intensity of the Raman Light Scattering on Polaritons in a Gallium Phosphide Crystal
Аннотация
Raman light scattering on phonons and polaritons is measured in a gallium phosphide sample. An unfocused beam of a 532-nm single-mode laser was used for excitation. A scattered radiation was collected using a mobile mirror of a small diameter, which allowed us to measure spectra of scattered light in a 0.6°–8° range of scattering angles with a total angular spread of 0.4°. For different crystallographic directions, intensities of polarized components of the Raman light scattering on longitudinal, transverse phonons and polaritons were measured in the region of a strong dispersion of the polaritonic branch for three fixed axial scattering angles. Components of scattering on longitudinal optical phonons and polaritons have a strong dependence on a crystallographic direction, as predicted by theory, and the component of scattering on transverse optical phonons did not depend on a crystallographic direction. It was found that the intensity of scattering on transverse optical phonons correlates with a width of a spectral line of scattering on polariton. A mechanism explaining this correlation is proposed.



Luminescent Properties of Europium(III) Compounds with Quinolinic Acid and Phosphorus-Containing Neutral Ligands
Аннотация
Luminescent mixed-ligand europium(III) complexes with quinolinic acid and phosphorus-containing neutral ligands with a dimeric structure of the composition Eu2(QA)3 · 3Н2О, Eu2(QA)3 · D · 2Н2О, where QA is quinolinic acid and D is hmpa (hexamethylphosphortriamide), tppo (triphenylphosphinoxide), (hmpa), or Et6pa (hexaethylphosphortriamide), are synthesized. The thermal and spectral-luminescent properties of the synthesized complex mixed-ligand europium(III) compounds are studied. It is shown that the detachment of water and neutral ligand molecules during thermolysis occurs in two stages with endothermic effects and that the complex compounds are stable at temperatures up to 320°С. It is found by IR spectroscopy that quinolinic acid coordinates to the europium(III) ion by two carboxylate ions. The low luminescence intensity of mixed-ligand europium(III) quinolinates is explained by inefficient electronic excitation energy transfer from quinolinic acid and phosphorus-containing neutral ligands to europium ions.



Spectroscopic Characteristics of Polymer Films Activated by a Supramolecular Nanodiamond Complex of Europium with Bathophenanthroline
Аннотация
New high efficiency luminescence films that convert UV radiation in a wavelength range of 220–410 nm into the europium ion luminescence are first obtained using a supramolecular diamond-containing complex of europium(III) with bathophenanthroline. The films allow the degree of radiation monochromaticity to be tuned at the main band of Eu3+ ions, centered at 615 nm. The excitation spectrum profile, as well as the half-width of the main emission band at 615 nm (a 5D0–7F2 transition) and the quantum yield values (in a range of ~0.3–0.8), is found to depend on the type of matrix material. The optical materials presented in the present work are promising candidates for the design of various light-emitting devices, such as screens, indicators, solar concentrators, organic LEDs, and laser media.



Spectral-Luminescent Properties of Some Benzaldehyde Derivatives
Аннотация
Substituted benzaldehydes, which are widespread in nature, exhibit antibacterial, anti-inflammatory, antiviral, and anticarcinogenic activity with low toxicity, which makes them promising in medicine. The results of an experimental and theoretical study of the spectral-luminescent properties of four neutral forms of hydroxy- and methoxy-substituted benzaldehydes are presented. The absorption spectra of the studied compounds in hexane and ethanol were obtained. The spectra of fluorescence and fluorescence excitation of the substances in ethanol solutions were measured. Based on quantum chemical calculations, the orbital nature of electronic transitions, the features of the electron density distribution upon excitation, and changes in the structure of the compound are determined and the rate constants of photophysical processes are estimated. According to calculations, in all the compounds studied, the S1 state is formed by the nπ* transition and the intensity of the long-wavelength bands in these compounds is formed by one or two ππ* transitions. The fluorescence quantum yield is estimated from experimental and theoretical data. The results of analysis and comparison of experimental data with the results of quantum chemical calculations allow a conclusion that the neutral forms of the studied substituted benzaldehydes are not responsible for the fluorescence observed in experiments with ethanol solutions.



The Effect of Nonequilibrium Synthesis Conditions on the Structure and Optical Properties of Amorphous Carbon Films
Аннотация
Amorphous carbon (a-C) thin films are synthesized using a nonequilibrium method of ion-plasma sputtering of a graphite target under argon atmosphere at a constant plasma current. The local structure of carbon films is studied by the Raman spectroscopy method. Using the normal distribution in the decomposition of the Raman spectra, it is found that a peak typical for a phonon density of states with sp3 bond hybridization appears in the frequency region of 1260 cm–1 at synthesis temperatures of less than 150°C. In addition, the influence of the dimensions of nanostructures composed of sp2 sites on the width of optical bandgap and their correlation with the results of X-ray photoelectron spectroscopy (XPS) in a-C films is shown.



Observation of Coherent Population Trapping in Ensembles of Diamond NV-Centers under Ground-State Level Anticrossing Conditions
Аннотация



A Study of Plasmon-Coupled Fluorescence of Rhodamine 6G on Thin Nickel Films
Аннотация
Plasmon-coupled luminescence of rhodamine 6G dye molecules on a thin nickel film has been studied experimentally and theoretically. The spatial distribution of fluorescence of dye molecules, which is calculated using the transfer matrix method for describing flat-layered media, is in good agreement with the experimental diagrams obtained for the spatial distribution of radiation with different polarization. The coupling efficiency between the luminophore and nickel film plasmons is experimentally determined.



Physical Optics
Detection of Weak Optical Anisotropy in Strontium Tetraborate Activated by Ytterbium Ions
Аннотация
A technique for detecting and measuring the weak optical anisotropy has been proposed and experimentally implemented. The strontium tetraborate activated by ytterbium ions, which is considered to be an amorphous glass, has been investigated and its anisotropy comparable with the instrumental errors of ellipsometer goniometers has been found and measured. The proposed approach is based on a previously developed effective and relatively simple method, in which the contribution of the surface (transition) layer to the formation of the resulting beam is essentially smaller than the contribution of the bulk material. The relations between the ellipsometer measuring zones have been used. Some important aspects of the optical and mechanical alignment of the ellipsometers have been described as applied to the weak anisotropy investigations.



Lasing of a Quantum-Cascade Laser with a Thin Upper Cladding
Аннотация
We present the results of experiments on the fabrication and study of the properties of quantum-cascade lasers of the spectral range of 7–8 μm in the geometry of a waveguide with a thin top cladding based on indium phosphide. The heterostructure is synthesized by molecular beam epitaxy on an InP substrate with an active region based on a heteropair of In0.53Ga0.47As/Al0.48In0.52As solid alloys. Laser emission at a wavelength of 7.8 μm at a temperature of 300 K with a threshold current density of ~6 kA/cm2 was achieved. The values of characteristic temperatures T0 and T1 for the studied quantum-cascade lasers are of the order of 150 and 450 K, respectively. The results obtained confirm that the design of the waveguide with a thin top cladding for devices for detecting liquids, the fabrication of microfluidic devices, and photonic circuits on silicon holds promise.



The Quasi-optical Equation in Media with Weak Absorption
Аннотация



Nonlinear Optics
Asymptotic Expansion of the Polarization Spectrum of a Two-Level System in a Polychromatic Field in the Small-Amplitude Limit
Аннотация
The impact of a polychromatic field on a two-level medium is considered in the limit of small amplitudes. In the indicated limit, we obtained asymptotic expansions of the polarization spectra of an arbitrary order of smallness. These polarization spectra were compared with the results of the numerical solution of the density matrix equation. Compared to numerical calculation methods, the asymptotic expansion offers an analytical estimation of the contribution of each individual component of a polychromatic field and a description of the intermode interaction. However, with an increase in the intensity of the driving field, the computational efficiency of the method decreases, since, to achieve the required accuracy, it is necessary to increase the order of the asymptotic expansion.



Low- and High-Order Nonlinear Optical Characterization of Metal Sulfide Quantum Dots
Аннотация
Any new synthesized semiconductor nanoparticles or quantum dots (QDs) require to be examined under different conditions using laser pulses of variable energies, wavelengths and durations to understand the nonlinear optical mechanisms and distinguish their attractive properties for practical applications. Among various QDs, the metal sulfides took special attention due to their advanced nonlinear optical properties. Additionally, laser ablation can readily produce plasmas containing QDs that could be used for different applications. One of them is that they can be used as emitters for harmonic generation from ultrashort laser pulses. Here we review recent studies of different low- and high-order optical nonlinearities of metal sulfide QDs, such as optical limiting, two-photon, saturable and reverse saturable types of nonlinear absorption, nonlinear refraction, and generation of high-order harmonics in extreme ultraviolet range.



Optical Materials
Transparent Photoactive ZnO–MgO–Ag2O Films on Glasses
Аннотация
Transparent ZnO–MgO–Ag2O coatings are formed on glasses by the polymer–salt method, and the optical properties of these coatings are studied. The optical properties of the films are studied by optical spectroscopy and photoluminescence. The structure of the oxide coatings is studied by X-ray diffraction analysis and scanning electron microscopy. It is found that an increase in the silver concentration in the coatings leads to a decrease in the band gap width of the material. It is shown that the films are characterized by a high transparency in the visible spectral region and can generate singlet oxygen under action of UV radiation (370 nm) and blue light (405 nm).



Optical Sensors and Transducers
Midinfrared Light-Emitting Diodes Based on А3В5 Heterostructures in Gas-Analyzer-Equipment Engineering: Potential and Applications in 2014–2018
Аннотация
Studies published in the period from 2014 to 2018 that are aimed at creating nondispersive and photoacoustic IR gas analyzers with LED radiation sources based on А3В5 heterostructures and operating in a range of wavelengths from 3 to 5 μm are reviewed. Potential of gas analysis equipment based on the aforementioned LEDs for detecting CO, CO2, methane, and other gases is analyzed.



Optics of Surfaces and Interfaces
Interaction of an Electromagnetic H Wave with a Thin Metal Film on a Dielectric Substrate in the Case of an Anisotropic Fermi Metal Surface
Аннотация
The interaction of an electromagnetic H wave with a thin metal film has been calculated with allowance for the ellipsoidal Fermi surface and constancy of the electron mean free path for different angles of incidence of the electromagnetic wave θ and different coefficients of specular reflection q1 and q2 at reflection of electrons from the film surfaces. The metal film is between two media with permittivities ε1 and ε2. The dependences of reflectance R, transmission T, and absorption A on the effective mass of conduction electrons have been analyzed.



Optical Communication, Optical Informatics, and Optical Computations
Spectrally Improved Controllable Frequency Comb Quantum Memory
Аннотация
We propose a scheme of a universal block of broadband quantum memory consisting of three ring microresonators forming a controllable frequency comb and interacting with each other and with a common waveguide. We find the optimal parameters of the microresonators showing the possibility of highly efficient storage of light fields in this memory block and we demonstrate the procedure for gluing several memory blocks for increasing the spectral range of the composite quantum memory while maintaining high efficiency.



Nanophotonics
Determining the Compositional Profile of HgTe/CdxHg1 – xTe Quantum Wells by Single-Wavelength Ellipsometry
Аннотация
An ellipsometric method for reconstructing the thickness compositional profile in thin heterostructure nanolayers grown by molecular beam epitaxy on the basis of a cadmium–mercury–tellurium compound has been developed. The method is based on solving an inverse ellipsometric problem with the replacement of part of an inhomogeneous layer with a homogeneous medium with specially selected optical constants. The numerical simulation has confirmed the correctness of this replacement and efficiency of the developed algorithm. Using this method, the active region of a heterostructure consisting of five HgTe quantum wells separated by wide-gap CdHgTe spacers has been investigated. Based on the results of continuous in situ ellipsometry measurements performed during the heterostructure growth, the compositional profiles for all the five sequentially grown quantum wells have been calculated and the high reproducibility of the thickness dependences of their composition has been demonstrated.



A Method for Estimating the Functionality of TiO2/Quantum Dot Multilayer Hybrid Structures Based on the Generation of Reactive Oxygen Species
Аннотация
A new technique for estimating the efficiency of electron transfer from a CdSe/ZnS quantum dot (QD) to TiO2 nanoparticles based on the generation of reactive oxygen species by hybrid structures is presented. It was demonstrated that in the formed multilayer hybrid structures of TiO2/QD, photoinduced electron transfer is realized with an efficiency of 26%.



Biophotonics
Optical Clearing of Human Skin Using Some Monosaccharides in vivo
Аннотация
We present the results of in vivo optical immersion clearing of human skin by aqueous solutions of some immersion agents (ribose, glucose, and fructose monosaccharides and glycerol), obtained using optical coherence tomography (OCT). To assess the efficiency of optical clearing, we determined the values of the rate of change of the light scattering coefficient, obtained using the averaged A-scan of the OCT signal in the derma section at a depth of 350–700 μm. A good correlation was observed between the rate of change of the light scattering coefficient and the potential of the optical clearing. Using complex molecular simulation of the interaction of a number of immersion clearing agents with collagen mimetic peptide (GPH)3 using classical molecular dynamics and quantum chemistry, we found correlations between the efficiency of optical clearing and the energy of intermolecular interaction of cleaning agents with a fragment of collagen peptide.



Applied Optics
Monitoring of the Process of Immersion Optical Clearing of Collagen Bundles Using Optical Coherence Tomography
Аннотация
Future development of the method of immersion optical clearing of biological tissues—this method is widely used in the study of the morphology and pathologies of tissues in vitro and considered promising for in vivo applications in biophysical research and medicine—requires knowledge of the details of interaction of immersion liquids with the tissue, in particular, the characteristics both of the tissue dehydration process, which is caused by the osmotic effect of the immersion liquid, and the process of diffusion of the immersion agent (IA) into the tissue. The optical properties of skin dermis, eye sclera, tendon, and many other tissues are determined by the properties of collagen bundles, abundant in these tissues. In the present work, a convenient and reliable technique for monitoring the optical properties and geometry of collagen bundles in the course of their immersion clearing in vitro, based on optical coherence tomography (OCT), is proposed. The main advantage of this technique is that it allows one to monitor changes in the geometric and optical properties of the tissue simultaneously, without interrupting the natural course of the immersion clearing process, and to obtain reliable estimates of the characteristic times and rates of both the process of tissue dehydration and process of diffusion of the IA into the tissue.



Full-Field Optical Coherence Tomography Based on a MII-4 Microprofilometer Using Microlenses with Air Immersion
Аннотация
A modernized Linnik microprofilometer (MII-4) allowing the performing of tomographic investigation of transparent and relatively turbid media by the methods of low-coherence interferometry has been presented. The design of the reference channel of the standard MII-4 has been revised. A dynamic adjustment of the reference arm length has been added to compensate for the effect of divergence between focal and coherent volumes, as well as spherical aberration that occurs when the optical system is focused into the deep layers of the object without the use of immersion microlenses. The analysis of the existing technical solutions of the reference arm designs has been carried out and their main drawbacks have been indicated. All stages of assembly and alignment of the complex have been described, and the device operation during visualization of transparent and turbid layered objects has been demonstrated.


