We calculated the probabilities of two-step schemes (optical cycles) for the transfer of polar RbYb and CsYb molecules from highly excited vibrational states to their ground vibronic state. It is shown that the most effective optical cycles can be realized using the excited 2²Σ⁺ state.

LiNbO_3congr and LiNbO₃:Mg (0.19÷5.91 mol. %) crystals were studied using IR and Raman spectroscopy. The intensities of the bonds corresponding to the stretching vibrations of the ОН groups in IR spectra increased or disappeared in LiNbO₃:Mg crystals with the growth of the Mg concentration. This could be explained by the disappearance of the ОН groups near Nb_Li⁴⁺-V_Li¯ defects due to the displacement of Nb_Li defects by Mg cations. At the same time, the Raman bands corresponding to the oxygen atom vibrations in oxygen octahedrons and the bridge-valence vibrations of oxygen atoms are wider for LiNbO₃:Mg (5.1 mol.%) than for LiNbO_3congr. This widening could be explained by octahedra deformation, determined both by the increase of the Mg concentration and the change of the proton localization. The suppression of the photorefractive effect in LiNbO₃:Mg crystals doped by magnesium higher threshold concentrations could be explained by the change of the proton localization and the screening of the bulk charge field.

Two-ring aromatics, such as naphthalene, are important fluorescent components of kerosene in the planar laser induced fluorescent (PLIF) technique. Quantifying measurements of kerosene vapor concentrations by PLIF require a prior knowledge of the fluorescence intensity of naphthalene over a wide temperature and oxygen concentration range. To promote the application of PLIF, a semi-empirical formula based on the collision theory and experimental data at the laser wavelength of 266 nm and a pressure of 0.1 MPa is established to predict the fluorescence intensity of naphthalene at different temperatures and oxygen concentrations. This formula takes vibrational states, temperature, and oxygen quenching into account. Verified by published experimental data, the formula can predict the fluorescence intensity of naphthalene with an error less than 9%.

We investigated the photoluminescent properties of nanocomposites based on the liquid crystal (LC) 5CB filled with dispersed inorganic particles, such as carbon nanotubes (CNT), montmorillonite mineral platelets (MMT) and titanium dioxide nanotubes TiO₂ (TNT), in the temperature range 4.2-300 K. The IR absorption spectra of these composites were studied in the spectral range 390-4000 cm^-1 at room temperature. The composite luminescent properties depending on the physical properties of the nanoparticles were considered. The long-wavelength shifts of the composites luminescence spectra according to the 5CB spectrum were defined by the magnitude of the nanoparticles specific surface. The spectral long-wavelength shifts at room and low temperatures were analyzed.

The Rayleigh-Brillouin light scattering in the chalcogenide glasses of the Ge-Sb-S system in the (Sb₂S₃)_х×(GeS₂)_100-х (х = 0-50) set is investigated. The longitudinal hypersonic velocity, the high-frequency longitudinal elastic modulus, the extinction coefficient at the wavelength l = 0.6328 μm, and the Landau-Placzek ratio are determined. The Landau-Placzek ratio for the glassy alloys of the Ge-Sb-S system depends strongly on the average coordination number and becomes maximal at Z = 2.67.

The paper presents the results of the study of the effect exerted by exciting laser radiation on the Raman spectra of synthetic diamond single crystals plates (linear dimensions from 3х3 to 5х5 mm) having different impurity compositions. It has been found that an increase in the power of laser radiation from 70 to 480 mW (90-600 kW/cm²) leads to heating of the samples by a few tens of degrees, which results in shifting of the Raman line maxima by ~ 0.5 cm^{- 1} and in the increased Raman line half-width up to ~ 0.15 cm^{- 1} . As demonstrated by the spectral data, the heating temperature correlates with the optical density and geometry of the samples and also with the conditions of heat extraction from their surface. Based on the independent measurements of the crystal temperature at a certain distance from the excitation beam axis, it is shown that the variations of the characteristics of the principal Raman line are not determined by the local heating of the crystal studied under the effect of laser radiation. An analysis of the characteristics of the Stokes and anti-Stokes spectral components makes it possible to separate the temperature and impurity effects in the variations of the principal Raman line. Using diamond monocrystalline samples as an example, it has been revealed that the increased content of nitrogen as an impurity in the lattice from 3 up to 200 ppm leads to shifting of the Raman line maximum towards lower wave numbers by ~0.08 cm^{- 1} and to its broadening by ~0.23 cm^{- 1} .

We developed a feasible model for the ab initio calculation of the phonon properties of three-component solid solutions of transition metal dichalcogenides. This model is based on the assumption of equal displacement of same-type chalcogen atoms and decoupled displacement of metal atoms. The results of phonon frequency calculation for monomolecular layers MoS_2-xSe_x and MoS_2-xTe_x at the Г-point are in conformity with the existing experiment data of Raman spectroscopy.

Methods of fabrication of solid-phase composite Ag- and Au-containing nanostructured systems with a shell of photochromic diarylethenes molecules (DAE) have been developed. The samples of nanocomposite systems were obtained. These nanocomposites exhibit photochromic properties similar to the properties of DAE in solution and solid-phase layers not containing metal nanoparticles. A chemical interaction between nanoparticles and sulfur-containing derivatives of DAE in solid-phase nanocomposites was detected.

A method to disperse multi-walled carbon nanotubes in a two-component SpeciFix-20 polymer (epoxy resin + hardener) using joint hydromechanical and ultrasonic mixing was developed. New composite materials with carbon nanotubes in the epoxy polymer were produced. The structure, optical and electrical characteristics of these composites were studied. Propagation of electromagnetic radiation in the experimental samples of composite materials was investigated in the microwave range (26-38 GHz). It was shown that strong absorbtion of the composite material appeared only with significant additions of multiwalled carbon nanotubes and was caused by the appearance of electrical conductivity of the composites. A “size effect” was established for the influence of the addition type on the optical characteristics of the resulting composite materials. Being dependent on the carbon nanotubes specific surface, electromagnetic radiation absorption increases with the nanotube percentage and the decreasing of nanotube diameter.

The appearance of a new type of electronic excitations in heterostructures with semiconductor and dielectric quantum dots - excitons formed by spatially separated electrons and holes - was considered. In the heterostructures containing semiconductor and dielectric quantum dots, the effect of a substantial increase in the binding energy of such exciton was observed (a hole moves in the volume of a quantum dot, and an electron is localized over a spherical interface between a quantum dot and matrix) in comparison with the exciton binding energy in semiconductor and dielectric monocrystals.

A quasi-classical model of the negative trion (exciton + electron) decay in a single crystalline quantum well (QW) into a c-band electron and the exciton followed by a recombination of the electron and hole constituting the exciton was developed. It was shown that the trion binding energy increases when the QW quantum-size energy levels are filled with electrons from the semiconductor matrix selectively doped with donors. It was established by calculations that the width of the trion emission line is slightly larger than that for a single exciton. On the whole, the obtained results agree with the known experimental data on low-temperature radiative decay of trions in QW. It was pointed out on the possibility of change of the trion quantum-size energy levels population under the action of a longitudinal (along the QW) electric field. A scheme of a stationary light-emitting device based on radiative transitions of trions (that not leading to their decay) between quantum-size energy levels was proposed.

Spectra and structure of near-surface plasma were experimentally studied and recoil momenta were measured at a double-pulse laser action on brass and graphite targets in air at wavelengths of 0.532 and 1.064 μm, depending on the time interval between laser pulses and their order of following in time. The laser plasma temperature, the electron concentration, and the recoil momentum were found depending on the parameters of double laser pulses at a laser power density of 4·10⁹ W/cm² It is shown that the optimal conditions for recording the erosion plasma spectra are such that the first pulse is generated at the second harmonic with a peak-to-peak time interval of 1.5-6 μs, whereas to produce an optimized recoil pulse, this interval should be shorter (1.5-2 μs). This is important for increasing the efficiency of emission laser spectral analysis and laser-plasma micromotors for space applications.

Foliar nitrogen (N) is an important index to evaluate the content of nitrogen in rubber trees. Hence, a fast way utilizing the spectroscopy to estimate the nitrogen content level of the rubber tree under natural environment has been preliminarily investigated in this paper. The combined features strategy is adopted in this study. The evaluation model is developed by back propagation (BP) algorithm and Adaboost algorithm. The results of simulation experiment show that satisfactory classification performance has been achieved using the proposed model and the percentage of samples correctly classified by the proposed model in the validation set is 92.98%.

The influence of the second amino acid on the pH response of the genetically encoded pH indicators is studied. The second Trp has been substituted by Ala and Glu to reduce self-quenching. Compared with the previously reported Trp-Trp-Ala-Ser (WWAS), the two new tetrapeptides, Trp-Ala-Ala-Ser (WAAS) and Trp-Glu-Ala-Ser (WEAS), have higher fluorescence quantum yields, longer fluorescence lifetimes, and more sensitive pH responses. As novel genetically encoded pH indicators, the N-terminal Trp-Ala and Trp-Glu could be fused to proteins for monitoring the environmental pH values during the studies of functional proteins.

For the determination of nitrogen oxides in the air, the structure of diazo and coupling compounds was studied and tested by experiments. The conditions and methods of diazo and coupling reactions were investigated. Furthermore, a spectrophotometric method using sulfanilamide as a diazo compound and 2-N-ethyl-5-naphthol-7-sulfonic acid (N-ethyl J acid) as a coupling compound was proposed. The maximum absorption wavelength of Sulfanilamide-N-ethyl J acid azo compound was at 478 nm. The molar absorptivity was 4.31×10⁴ L/(mol × cm) with a recovery of 98.7-100.9% and RSD of 1.85%. For nitrogen oxides, the determinate limit of this measurement was 0.015 mg/m³ and the determinate range 0.024-2.0 mg/m³. Moreover, a high degree of correlation was observed between the results obtained by the proposed method and the standard methods. The proposed method can be easily applied to determine nitrogen oxides in the air.

An investigation of the paramagnetic properties of lichens using the EPR-spectroscopy method was carried out for Xanthoria parietina (L.) Th. Fr as a case study. It was shown that the increase of the air pollution level leads to higher concentration of paramagnetic centers in lichen thallus. Possible mechanisms of the paramagnetic centers formation in lichen were discussed. The efficiency of the EPR spectroscopy method in studying lichens as environmental quality indicators was demonstrated.

The possibility of using Raman spectroscopy to determine chemical reaction rates and activation energies is shown under saponification of ethyl acetate, as an example. The reaction rate depending on temperature has been measured for the interval of 15-45°C.

The results of investigating electrical, power and spectral radiation properties of an experimental three-electrode xenon flash lamp are presented. The lamp was operated at high-pressure in the regimes close to the maximum spectral brightness limit of xenon emission. It was shown that in the regime of saturated brightness (the black-body temperature in the visible spectral range ~30000 К) the radiation of the pulsed discharge in xenon differs significantly from the radiation of an absolutely black body: the maximum black-body temperatures were 24000 and 19000 K for UV and near IR ranges, respectively. The relative portion of UV radiation in the lamp emission spectrum is more than 50%, which allows to consider such lamps as promising broadband radiation sources of high spectral brightness for many actual practical applications.

A scheme of the multi-channel continuous scan Fourier spectrometer is proposed for simultaneous recording and analysis of the spectral characteristics of several objects. The scheme is realized using a multi-probe fiber in which several optical fibers are connected in one optical connector and fixed in the output of an interferometer. The Fourier spectrometer is used as a sygnal modulator. Еach fiber is individually mated with the studied sample and its own radiation detector. For the developed system, the spectrometer aperture is calculated from the condition of the minimum spectral resolution and parameters of the optical fibers. With the help of the proposed scheme, the emission spectra of a gas-discharge neon lamp have been recorded using a single fiber with a diameter of 1 mm and a numerical aperture NA = 0.22.

The equality of the probabilities of direct and inverse electron-vibrational transitions between the initial and final elementary quantum Franck-Condon states in the adiabatic approximation is taken as the equality of the probabilities of one electronic transition, in which only the initial and final elementary vibrational ensembles exchange places. Frequencies of the transitions will have mirror symmetry with respect to 0-0-transition frequency n₀. Accounting for this and the selection of "hot" molecules in the anti-Stokes regions under thermal equilibrium in the initial state leads to a "restoration" of the known relation for the cross sections of the transition s(n) the form: (s(n)/n)exp(±hn/2kT) = j((n - n₀)²), where “+”is for emission, “-“ is for absorption. Examples of the relation use for the determination of n₀ from the absorption, fluorescence and phosphorescence spectra are given and a comparison is made with n₀ obtained by jet-cooling.

The films of europium doped yttrium alumina composites (YAG:Eu) with europium concentration 0.020, 0.025, 0.030 M were synthesized using the sol-gel technique. The films were fabricated by spinning on fused silica followed by heat treatment. It is shown, that after the heat treatment within the temperature range of 800-1200 °С for 30 min the films reveal luminescence bands in the visible range, corresponding to the optical transitions⁵D₀ →⁷F_j (j=0,..,4) of trivalent erbium ions. The films are X-ray amorphous, whereas the powder formed from one of the used sols with europium concentration of 0.02 M is in crystalline phase Y₃Al₅O₁₂ after the heat treatment at 1000°C. The practical application of the obtained europium doped yttrium alumina composites as converters transforming ultraviolet irradiation into visible range and for other photonic structures is discussed.

Transmittance spectrum of ZnSe in the infrared and visible wavelength range at normal incidence was investigated by an IRTracer-100 spectrometer and a TU-19 Double-BeamVisible spectrophotometer, and the optical constants of ZnSe were obtained based on modelling transmittances of two ZnSe slabs. The results show that the transmittance values of the ZnSe slabs are higher than 0.7 in the wavelength range of 2.5-15 mm; however they decrease dramatically when the wavelength is larger than 15 mm. The refractive index of ZnSe varies within 2.6-2.8 in the wavelength range of 0.55-0.85 mm and 2.2-2.4 in the wavelength range of 2.5-20 mm. The extinction coefficient of ZnSe varies within 10^-8-10^-6 in the wavelength range of 0.55-0.85 mm and 10^-5-10^-4 in the wavelength range of 2.5-20 mm.

The oxygen deficient polycrystalline La_0.70Sr_0.30MnO_3-g (0 < g £ 0.2) manganites were studied by means of electron magnetic resonance (EMR). The EMR spectra give evidence for an unusual and g-dependent transition between the ferromagnetic and paramagnetic phases of the manganites. A Griffiths phase (revealed as coexisting ferromagnetic and paramagnetic signals far above the magnetic ordering temperature) was observed in the samples with 0.1 £ g £ 0.2. The formation of this phase, characterized by the existence of ferromagnetic clusters in the paramagnetic matrix, is caused by oxygen deficiency which hampers the realization of long-range ferromagnetic ordering of manganese ions.

3-(3,4-Dimethoxyphenyl)-1-(2,5-dimethylfuran-3-yl)prop-2-en-1-one (DDFP) was prepared by the reaction of 3-acetyl-2,5-dimethylfuran and 3,4-dimethoxybenzaldehyde. Data obtained from FT-IR,¹H-NMR,¹³C-NMR, EI-MS, and elemental analysis were consistent with the chemical structure of the newly prepared DDFP. Electronic absorption and emission spectrum of DDFP have been measured in different solvents; DDFP dye exhibits red shift in emission spectrum as solvent polarity increases, indicating a large change in dipole moment of DDFP molecule upon excitation due to intramolecular charge transfer in excited DDFP. Excited state intermolecular hydrogen bonding affects the energy of emission spectrum and fluorescence quantum yield of DDFP molecule. DDFP dye undergoes solubilization in different micelles and may be used as a probe or quencher to determine the critical micelle concentration (CMC) of CTAB and SDS. The photoreactivity and net photochemical quantum yield (f_c) of DDFP are determined in solvents CHCl₃, CH₂Cl₂, CCl₄, and DMSO. The dye is relatively photostable in DMSO and displays photodecomposition in chloromethane solvents.

Two spectrophotometric methods were developed and validated for the determination of rifampicin (RIF) in bulk form, formulations, and spiked human urine. The first method is based on the reduction of the Folin-Ciocalteu (FC) reagent by RIF to form a blue colored chromogen with l_max at 760 nm (the FCR method). In the second method, iron(III) is reduced by RIF in a neutral medium, and the resulting iron(II) is complexed with ferricyanide to form a Prussian blue peaking at 750 nm (the FFC method). Under optimum conditions, Beer’s law enabled the determination of the drug in the concentration ranges 1-35 and 2.5-50 µg/mL with apparent molar absorptivities of 2.72×10⁴ and 1.63×10⁴ L/(mol × cm) for the FCR and FFC methods, respectively. The Sandell sensitivity, limits of detection (LOD), and quantification (LOQ) values were also reported for both methods. The precision of the methods, with % RSD of < 2%, was satisfactory, and the accuracy was higher than 2% (RE). The proposed methods were successfully applied to the determination of drug in capsules without interference from common additives and spiked human urine without interference from endogenous substances. A statistical analysis indicated that there was no significant difference between the results obtained by the developed methods and the official method.

Near infrared spectroscopy and the back propagation artificial neural network model in conjunction with backward interval partial least squares algorithm were used to estimate the purchasing price of Enshi yulu young tea shoots. The near infrared spectra regions most relevant to the tea shoots price model (5700.5-5935.8, 7613.6-7848.9, 8091.8-8327.1, 8331-8566.2, 9287.5-9522.5, and 9526.6-9761.9 cm^-1) were selected using backward interval partial least squares algorithm. The first five principal components that explained 99.96% of the variability in those selected spectral data were then used to calibrate the back propagation artificial neural tea shoots purchasing price model. The performance of this model (coefficient of determination for prediction 0.9724; root mean square error of prediction 4.727) was superior to those of the back propagation artificial neural model (coefficient of determination for prediction 0.8653, root mean square error of prediction 5.125) and the backward interval partial least squares model (coefficient of determination for prediction 0.5932, root mean square error of prediction 25.125). The acquisition price model with the combined backward interval partial least squares-back propagation artificial neural network algorithms can evaluate the price of Enshi yulu tea shoots accurately, quickly and objectively.

A rapid and convenient near infrared (NIR) reflectance spectroscopic procedure for the determination of metformin hydrochloride in tablets is presented. Determination was based on calibration curves that were obtained using a range of standards containing different concentrations of metformin hydrochloride blended with polyvinylpyrrolidone. The raw spectra of the standards, neat PVP, metformin hydrochloride, and powdered tablets were processed using a Multiplicative Scatter Correction filter as well as by the derivative spectroscopy method to give a basis for the calibration curve construction. The results were validated by thin-layer chromatography followed by UV-densitometry.

Сhitosan-zinc oxide nanoparticles (CZPs) were developed for solid-phase extraction. Combined artificial neural network-ant colony optimization (ANN-ACO) was used for the simultaneous preconcentration and determination of lead (Pb²⁺) ions in water samples prior to graphite furnace atomic absorption spectrometry (GF AAS). The solution pH, mass of adsorbent CZPs, amount of 1-(2-pyridylazo)-2-naphthol (PAN), which was used as a complexing agent, eluent volume, eluent concentration, and flow rates of sample and eluent were used as input parameters of the ANN model, and the percentage of extracted Pb²⁺ ions was used as the output variable of the model. A multi-layer perception network with a back-propagation learning algorithm was used to fit the experimental data. The optimum conditions were obtained based on the ACO. Under the optimized conditions, the limit of detection for Pb²⁺ ions was found to be 0.078 µg/L. This procedure was also successfully used to determine the amounts of Pb²⁺ ions in various natural water samples.

A procedure for matrix effect reduction is proposed to enhance the precision of quantitative analysis of metal alloys using laser-induced breakdown spectroscopy (LIBS). This procedure is based on a number of successive steps in order to correct the signal fluctuations caused by plasma interaction and the matrix effect. The first step is the selection of optimum parameter settings of the detection system, such as laser power, delay time, and focal distance. The second step is the estimation of the absolute or relative values of impurities on the basis of the internal standard calibration. The third step is the analysis of the metal basis of the alloy used as an internal standard, which requires spectrum averaging, whole integral spectrum normalization, and self-absorption correction. Three sets of metal-based alloys (aluminum, steel, and copper) are used in this investigation as reference standards for calibration and validation. Successive improvements of the quality of calibration curves are observed during the proposed procedure.

Laser-induced breakdown spectroscopy (LIBS) coupled with the nonlinear multivariate regression method was applied to analyze magnesium (Mg) contents in soil. The plasma was generated using a 100 mJ Nd:YAG pulsed laser, and the spectra were acquired using a multi-channel spectrometer integrated with a CCD detector. The line at 383.8 nm was selected as the analysis line for Mg. The calibration model between the intensity of characteristic line and the concentration of Mg was constructed. The traditional calibration curve showed that the concentration of Mg was not only related to the line intensity of itself, but also to other elements in soil. The intensity of characteristic lines for Mg (Mg I 383.8 nm), manganese (Mn) (Mn I 403.1 nm), and iron (Fe) (Fe I 407.2 nm) were used as input data for nonlinear multivariate calculation. According to the results of nonlinear regression, the ternary nonlinear regression was the most appropriate of the studied models. A good agreement was observed between the actual concentration provided by inductively coupled plasma mass spectrometry (ICP-MS) and the predicted value obtained using the nonlinear multivariate regression model. The correlation coefficient between predicted concentration and the measured value was 0.987, while the root mean square error of calibration (RMSEC) and root mean square error of prediction (RMSEP) were reduced to 0.017% and 0.014%, respectively. The ratio of the standard deviation of the validation to the RMSEP increased to 8.79, and the relative error was below 1.21% for nine validation samples. This indicated that the multivariate model can obtain better predicted accuracy than the calibration curve. These results also suggest that the LIBS technique is a powerful tool for analyzing the micro-nutrient elements in soil by selecting calibration and validation samples with similar matrix composition.