The effect of pressure on the Raman spectrum of gaseous propane in the methane is investigated. It is found that if the density of environment increases, its Raman bands within the range 2700-3100 cm^-1 shift to lower wavenumbers, but the change of the bands in the range 300-1600 cm^-1 is negligible.

Novel amorphous perfluorinated polymers are synthesized and their features are investigated in terahertz and X-ray spectral ranges. We consider the features of the polymerization process for such monomers in which all hydrogen H atoms are replaced by fluorine F atoms. The measurements of their optical features in the THz range show a record low value of the refraction index in comparison with any solid. The possible minimum of the refraction indices for such polymers is estimated. Also the high transparency of these polymers is shown. The X-ray spectra for some of such polymers are measured. The data obtained by X-ray diffraction analysis are compared with the peaks of the terahertz absorption spectrum.

The processes of association of eosin molecules in AOT inverse micelles of different sizes have been studied. It is shown that as the hydrodynamic radius R_h of the micelle increases, the degree of association of the dye molecules increases. The structure of the formed associates (dimers) of eosin is determined. It is shown that an increase in R_h is accompanied by an increase of the angle a and a decrease of the distance between the dye molecules in the dimer.

The study is based on the determination of trace elements in ruby samples, Ti in particular, using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). The samples were then divided into three groups: high (≥200 ppma), moderate (100-200 ppma) and low (≤50 ppma) Ti content. In addition, X-ray absorption spectroscopy (XAS) was employed to confirm that the Ti oxidation state was Ti⁴⁺ . The heat experiment conditions were set at 800, 1200, and 1650ºC to investigate the transformation of the -OH vibration in the FTIR spectra of ruby samples. The FTIR spectra showed that samples containing a low Ti concentration did not show the 3309 cm^{- 1} absorption peak either before or after heating at any of the designed temperatures. An obvious 3309 cm^{- 1} peak appeared only in samples with a moderate to high Ti content after heating at ≥1200ºC. The results also suggest that, in addition Ti⁴⁺ , the occurrence of the 3309 cm^{- 1} peak in the FTIR spectra is strongly affected by the charge compensation of -OH in Al sites, i.e., the structural -OH; thus, the structural -Ti-OH stretching in the ruby samples. Hence, for gemological identification, the 3309 cm^{- 1} peak can be applied to indicate whether a ruby has undergone heat treatment if those samples contain enough Ti ions in their structure, i.e., Ti ≥ 100 ppma. This condition is usually found in ruby samples from major deposits such as Mong Hsu and Mogok, Myanmar; Luc Yen, Vietnam; and Montopuez, Mozambique.

The spectral complex of the fundamental optical functions of the strontium selenide crystal in the range 0-40 eV was determined. The spectra of the imaginary parts of three functions (the transverse dielectric permittivity ε₂(E), longitudinal volume -Imε^-1, and surface -Im(1+ε)^-1 characteristic electron energy losses) of the strontium selenide crystal were decomposed into 36 elementary bands. The energies of the maxima E_i, half-widths H_i, amplitudes I_i, areas S_i, and oscillator strengths f_i of each band were determined for the three spectra types. We determined the main features of the spectra of the optical functions and 36 elementary bands of strontium selenide due to excitons and interband transitions of the transverse and longitudinal types in the region of 3-35 eV. The calculations were performed on the basis of experimental reflection spectra using the Kramers-Kronig integral relations, the modified method of combined Argand diagrams and a number of computer programs.

It is found that the film composites of the copolymer of styrene with octylmethacrylate and dopants of monomers of pyrido[2,1-b]benzothiazole derivatives have a hole type of photoconductivity. Meanwhile, the internal photoelectric effect in this medium is determined by the photogeneration of carriers from monomers and the transfer of non-equilibrium carriers through these monomers. The photoconductivity and photovoltaic response increase for a monomer with a more efficient coupling system.

We present the analysis of wave functions and the effect of configuration interaction on the intensity of absorption bands for Pr³⁺ , Tm³⁺ , and Er³⁺ ions. It is shown that due to the strong spin-orbit interaction the wave functions of rare-earth ions are multicomponent superpositions of “pure”^{2S+ 1} L_J multiplets with different values of S and L and the same values of the angular momentum J. For this reason, the effect of configurational interaction depends not only on the energy gap up to excited configurations, but also on the presence of high-energy^{2S+ 1} L_J components. The presence of such components wields a strong influence on the configuration interaction even at the deep layers. Another consequence of the multicomponent composition of the wave functions is the formation of groups of strongly interrelated states. When the configuration interaction is not fully taken into account, the error in describing the oscillator strengths is distributed among all the states of the group, and the low overall accuracy of the description is not perceived as a contradiction to the theory. To confirm the proposed assumptions, the oscillator strengths of the absorption transitions of laser materials activated by Pr³⁺ , Tm³⁺, and Er³⁺ ions are described using the modified Judd-Ofelt theory.

The spectral and luminescence decay kinetics of magnesium aluminate spinel ceramics prepared by spark plasma sintering (SPS) technique and the starting nanopowders were studied. It was demonstrated that there are two types of luminescence in spinel ceramics can be observed after pulse e-beam excitation. The first type is intrinsic defects, and the second one responsible for Cr³⁺ and Mn²⁺ ions. It was shown that the luminescence decay kinetics for Cr³⁺ and Mn²⁺ impurity ions can be approximated by the sum of two exponents. The decay times for the Cr³⁺ ion are 35 and 409 ns, for the Mn²⁺ ion are 29 and 340 ns. High-temperature exposure during of SPS synthesis does not lead to a change in the nearest surroundings of impurity ions. In the luminescence spectra of ceramic and powder samples the intensity ratio changes of intrinsic and impurity centers and this is associated with strong diffuse scattering of light for spinel nanopowders.

Films of undoped ZnO and of ZnO/C nanocomposite were formed by the sol-gel method on glass substrates and on fiberglass using zinc acetate as a precursor and adding zinc chloride into it, respectively. Analysis of the photoluminescence spectra of ZnO/C films at high (N₂-laser) and low (HeCd-laser) excitation levels made it possible to establish the defining role of bound excitons in the photoluminescence at 20-60 K, due to the presence of chlorine residues in the films. With the temperature increase to 300 K the role of recombination through 1LO- and 2LO-phonon replicas of free exciton levels and impurity levels begins to dominate in photoluminescence of ZnO/C films.

Two spectrofluorometric methods are developed and optimized for the determination of substituted benzamides, namely itopride hydrochloride (ITO), alizapride (ALI), and mosapride citrate (MOS), in drug substances and pharmaceutical formulations. The first method is based on the measurement of the relative fluorescence intensity of the cited drugs in the absence of methyl-β-cyclodextrin at 380±2 nm using an excitation wavelength of 310 nm in an aqueous solution. The linearity ranges were found to be 0.05-10, 0.1-10, and 0.1-10 μg/mL, with mean recoveries of 100.04% ± 0.21, 100.06% ±0.65, and 100.08 %±0.26 for ITO, ALI, and MOS, respectively. The second method is based on the significant enhancement of the fluorescence intensities of the drugs produced through complex formation with methyl-β-cyclodextrin in an aqueous solution at pH 6.6 in the case of ITO and pH 7.2 in the case of ALI and MOS. The fluorescence intensities of the formed complexes were measured at 420±2 nm using an excitation wavelength of 310 nm. The linearity ranges were found to be 5-35, 3-15, and 2-30 ng/mL, with mean recoveries of 100.22 ± 30, 100.12 ± 0.24, and 100.30 ± 0.44, and limits of detection of 1.98, 1.32, and 0.66 ng/mL for ITO, ALI, and MOS, respectively. 1:1 stoichiometries for β -CD-drugs complexes were established. Association constants and Gibbs free energy were calculated by applying the Benesi-Hildebrand equation. The results were found to agree statistically with those obtained from the reference methods.

We demonstrate the utility of 4-chloro-7-nitrobenzofurazan (NBD-Cl), a simple, low-cost probe, for colorimetrically and fluorescently detecting and differentiating similar thiol species, including cysteine, homocysteine, and glutathione, as well as for assaying acetylcholinesterase (AChE) activity. This assay is a potential tool for investigating thiol functions in disease and diagnosis, and for screening AChE inhibitors. We envision that this versatile probe, which is commercially available and inexpensive, will be useful for further elucidating the roles of thiols in biology and also shows applicability for analysis of AChE inhibitors in physiological samples.

It is established that groups of absorption bands corresponding to lipids, proteins, nucleic acids and sugars can be distinguished in the IR spectrum of saliva. A feature of the spectra of saliva is the presence of absorption bands of thiocyanate ions. When comparing the typical IR spectrum of saliva with the absorption spectra of albumin, glucose and lysozyme, the similarity of the 1700-1400 cm^{- 1} spectral region with the albumin spectrum and 1100-1040 cm^{- 1} spectral region with the spectra of glucose and lysozyme was noted. It is shown that the sugars are in saliva in a protein-related form. Correlations between the intensity of absorption bands in the IR spectrum of saliva and its biochemical composition are revealed.

The relation between the integral autocorrelation parameters of the optical spectra of solutions of multicomponent hydrocarbon media with their color characteristics is established. The obtained dependences make it possible to estimate color characteristics of solutions of nonideal multicomponent hydrocarbon media such as oil and high-boiling petroleum distillates by their optical spectra.

The results are presented of laser radiation energy measurements for a KTP- and KTA-based OPO IR lidar used for the remote gas analysis of the atmosphere in the spectral ranges of 1.8-2.5 and 3-4 μm. The lidar measurements of trace gases in the spectral ranges considered have been simulated. Echo signals of the IR broadband lidar in the above ranges are experimentally detected.

Monitoring the state of ground-based spectroscopic systems ensures high accuracy of atmospheric gas measurements and the possibility of using measurement data for validating satellite measurements and numerical models. Column-averaged carbon dioxide mixing ratios (XCO₂) can be used to assess the quality of spectroscopic measurements because its content is stable in the atmosphere. We retrieved the XCO₂ values from spectra measured by Fourier transform IR spectrometer Bruker 125HR (FTIR) between 2009 and 2017 at the Peterhof station (St. Petersburg, Russia). The total error of the FTIR CO₂ columns retrieval is 4.18±0.02% with 0.36±0.06% and 4.16±0.02% for random and systematic errors, respectively. The data obtained are compared with model calculations based on long-term observations at the Mauna Loa station. Various schemes for the inverse problem solving are analyzed, their comparison is made among themselves, and estimates of empirical random errors in the determination of XCO₂ are obtained. To improve the accuracy of XCO₂ measurements, it is recommended simultaneously with the atmospheric gases measurements to determine the error of the Fourier-spectrometer phase and the slope of the zero line of the spectrum, taking into account various continuum sources of errors.

A colorimetric visual detection for melamine in milk, based on tetracyclopentyl calix[4]pyrrole-tetrachlorobenzoquinone assembly, was demonstrated. Color changes from purple to yellow occurred when a melamine-tetrachlorobenzoquinone complex was formed under optimized conditions. The formation and stability of the complex in a borate buffer was studied in detail. A 1:1 stoichiometric ratio was verified with UV-vis spectrometry, and a stability constant of 1.78×10⁴ M^{- 1} was calculated using nonlinear fitting. The colorimetric visual detection was demonstrated for melamine in pure solution and in a spiked milk sample, with respective sensitivities as low as 25 and 50 ppb.

A theoretical approach is used to calculate wavelength dependence of displacement and velocity resolution in the technology of laser Doppler vibrometry (LDV). Mathematical description of a typical LDV system in the heterodyne arrangement is considered in this regard. Thermal noise and shot noise are assumed as the primary source of noise. Minimum target displacement and velocity which produce noise equivalent signal are considered as displacement and velocity resolution respectively. A theoretical linear relationship between laser wavelength and the mentioned resolutions is obtained when all other operational parameters of the LDV system are kept constant. The results of the present research are in good agreement with the earlier experimental researches conducted by others.

At chromatographic separation of substances with different chromophores using spectrophotometric detection, instead of preliminary calibration of the detector response to inaccessible (or hardly accessible) standard samples, an approach specific for triacylglycerines (TAG) is proposed. According to this approach, a wavelength similar to the isosbestic point (278 nm) was found for the TAG containing radicals of three types of isomeric conjugated octadecatrienoic acids (COA), which can be used to determine the ratio of the amounts of TAG with isomeric radicals without introducing correction factors for sensitivity of each substance. The procedure of mathematical processing of UV spectra of TAG containing COA radicals which allows detecting these points is proposed. The specificity of the TAG composition allows us to abandon the detection or use of highly labile individual compounds. The method is developed on the example of the seed oil of centranthus (“red valerian”, Centranthus DC.), the TAG of which are formed by two isomeric COA (a- and b-eleostearic) and pomegranate seed oil (Punica granatum L.) with radicals of another pair of COA (punicic and a-eleostearic).

We have made an apparatus, which allows measuring all variable fluorescence parameters accepted in PAM-fluorometry at a distance up to 0.6 m by using the fluorescence LED excitation and a photo-detector aperture of 25 mm. The apparatus working capacity is shown by an example of detecting the PAM-parameters of a plant in a hermetic container. The technique and apparatus use is proved for other cases.

The noncollinear acousto-optic filtration of quasi-nondiffracting Bessel light beams in uniaxial crystals have been investigated. The coupled wave equations for vector amplitudes of the incident Bessel light beam of o-type and of the diffracted beam of e-type are obtained. The expression is found for the diffraction efficiency depending on parameters of the interacting Bessel beams of o- and e-types and also on the value of overlap integrals. Using the overlap integrals it is shown that no matter the order of the Bessel light beams in the transversal phase-matching conditions of the diffracted waves in the range of optical spectrum of 0.4-1.1 mm for paratellurite crystals the transmission bandwidth of ~0.6 nm is reached.

The algorithm for processing lidar signals is considered, which provides concentration profiles of a fine aerosol component for the sensing paths with constant qualitative aerosol characteristics (particle size distribution in each aerosol mode, complex refractive index of particles) with no additional a priori information. Verification of the algorithm is performed using lidar data of the Institute of Physics, NAS of Belarus. The vertical profile of the volume concentration of fine particles obtained by the proposed algorithm is in good agreement with the results of its independent retrieval on the basis of simultaneous processing of the lidar and sun photometer data.

Optical properties of the asymmetric nanoring/ellipsoid dimers with breaking of geometric symmetry are investigated theoretically. A tunable high order surface plasmonic resonance is achieved. It is demonstrated that such high order resonances result from the plasmonic coupling between the modes of a nano-ellipsoid and of an asymmetric nanoring. Interestingly, a current loop is observed on the nanoellipsoid under coupling of the two nanostructures. The surface plasmonic resonance of this nanostructure can also produce enhanced local fields that can be applied in surface-enhanced spectroscopy and biosensing.

The transmission and reflection spectra of a one-dimensional photonic crystal structure with an insert of a monolayer of metallic nanoparticles are calculated by the transfer-matrix method. The influence of the monolayer parameters and location on the defect modes of the photon structure is investigated.

5-Methylfurfural was studied by vibrational (IR and Raman) spectroscopy and computational methods (DFT/B3LYP&MP2). FT-IR and FT-Raman spectra in KBr (at room temperature) were collected. Gaussian 09 and Spartan 08 programs were used for conformational analysis and calculations of molecular structure, torsional barrier, and vibrational spectral data for the 5MF molecule. The obtained results were used in the analysis of experimental vibrational spectra of 5MF molecule.

The effect of solvent on the structural, frontier orbital energies, global density-based descriptors, vibrational frequencies, and³¹P NMR chemical shifts was examined for the syn-Cp₂Ti(h²-C₆H₄-2-OMe)(PMe₃) complex by the self-consistent reaction field theory (SCRF) based on the polarizable continuum model (PCM). The studied spectroscopic parameters were correlated with the Kirkwood-Bauer-Magat equation (KBM). Also, the response of the global density-based descriptors (chemical potential and hardness) in the presence of external electric field was studied. EDA, QTAIM, ELF, LOL, and NBO analyses were used for illustration of the Ti-C bond in this complex.

A method based on the inhibition of plant esterase from pesticides has been proposed and validated for the determination of carbendazim residues in aqueous samples. After optimization in pH, temperature, and detection time, a lower detection limit of 0.105 μM was obtained in the linear range from 0.105 to 41.84 μM. Upon analysis of the detection mechanism, carbendazim was found to be binding to plant esterase via the van der Waals force and the hydrogen bond with a single binding site through an exothermic reaction. Moreover, the proposed method was satisfactorily applied to the analysis of carbendazim residues in different aqueous samples, obtaining a remarkably good agreement with the standardized reference method.

High heterogeneity solid woven fabric samples were investigated using laser-induced breakdown spectroscopy (LIBS) and chemometrics. Many emission lines were relevant to characterize this material at the surface and in deeper layers of fibers. Differences among dyes and fibers were clearly observed. The scores maps showed the possibility of comparing the chemical compositions of the dye and fiber independent of the print of fabric. Variations in the composition were verified by carrying out a pattern for mapping using a sophisticated LIBS system. This screening can provide a fast evaluation of samples and may associate this information with classification, authenticity or even for forensic analysis of fabric materials.

Semiempirical quantum chemistry methods offer a very interesting compromise between accuracy and computational complexity. The low frequency vibration modes of three crystalline materials, namely, polyethylene, poly(vinylidene fluoride) form II, and a-D-glucose, have been studied using the PM6 and PM7 Hamiltonians in order to assess the performance of NDDO methods in the interpretation of terahertz spectra. The results have been compared with the available experimental data and former calculations performed using alternative methods. NDDO calculations are in good qualitative or semiquantitative agreement with the experimentally observed terahertz spectra.

The glimepiride molecule was experimentally characterized using vibrational (FT-IR and laser-Raman) and NMR chemical shift spectroscopy. The molecule optimized structure, vibrational wavenumbers, and¹H and¹³C NMR isotropic chemical shifts were theoretically obtained with the DFT/B3LYP method at a 6-311++G(d,p) basis set. The theoretical geometric parameters, vibrational wavenumbers, and NMR cheical shifts were found to be consistent with experimental data and similar spectral results in the literature.

Confocal Raman microspectral imaging (CRMI) provides a versatile tool to extract biochemical information on histologically defined regions with improved spatial resolution and sensitivity. Here, we investigate spectral features and perform both uni- and multi-variate analyses to obtain precise correlation between the biochemical profile and histological architecture of ex vivo human skin tissue. The skin dermis layer is visualized by integrated images of collagen peaks at 855, 940, and 1248 cm^{- 1} , while the stratum corneum layer is described by chemical images of ceramides. Melanin accumulation patterns in epidermis are obtained by integration of 1375 and 1580 cm^{- 1} Raman peaks. In addition, distinct spectral features of the melanin precursor are revealed by certain Raman vibrations, which structurally characterize the molecular composition and organization of hair follicles. These results offer a unique insight into the skin histology, biochemistry, and biophysics, which provide the possibility of interpreting the underlying mechanisms of skin malignant processes.

ZnS films were synthesized onto ZnO seed layer by chemical bath deposition (CBD) and annealing at 500ºC. To prepare films, molar percentages of sulfur were chosen as 6, 7, and 8%. Working temperatures of ZnO seed layer and ZnS films were 50 ± 5 and 70 ± 5ºC, respectively. Differences in structural, optical, and morphological properties were measure on those films. EDX analysis shows that S:7% films had the maximum elemental sulfur ratio. All films have ZnS (hexzagonal) [110] preferential orientation with different FWHMs. The most obvious nanorod formations were observed in S:7% films. Additionally, S:6% films had higher optical transparency over 65% in the visible region. Photoluminescence spectrum showed that the broad blue and narrow green emission and intensity were changed upon sulfur inclusion.

Nanoparticles of BaMoO₄:Dy³⁺ co-doped with ions of metals (Li⁺ , Mn²⁺ , Mg²⁺ , and Bi³⁺ ) were synthesized using ethylene glycol at 140^oC. The synthesized samples were characterized by X-ray diffraction, and the XRD patterns were found to be in agreement with the tetragonal system according to JCPDS-72-0747 with space group I4₁/a. The average crystallite sizes of the nanoparticles <30 nm were calculated using Scherrer’s formula. Excitation-emission spectra and lifetime study of the nanoparticle luminescence were carried out subsequently. The BaMoO₄:Dy³⁺ nanoparticles co-doped with various metal ions (Li⁺ , Mn²⁺ , Mg²⁺ , and Bi³⁺ ) showed two emission peaks at 485 (blue) and 575 nm (yellow) in comparison with the host BaMoO₄ (490 and 545 nm). The effects of co-doped ions on the emission of Dy³⁺ were elucidated.