A non-equilibrium Auger-transition is investigated, which consists in the fact that a vacancy in the valence layer is filled in a time of ~ 10^-14 s with an electron of the probe, which receives the energy released as a result of the transition of a valence electron to the K-layer and emits it from the surface. For the first time, a non-equilibrium Auger-spectrum was obtained from the surface of thin (8–10 atomic layers) films of silver oxide Ag₂O on a Si₃N₄ substrate at a probe radiation energy of 8–10 keV. The probability of the escape of non-equilibrium Auger-electrons is analyzed depending on the atomic number. The characteristic amplitude peaks characterizing the contribution of non-equilibrium Auger-electrons to the recorded signal are established. Based on the mathematical model describing the dynamics of the non-equilibrium Auger-process, its probability, relaxation time, and also the cross section for the capture of a free carrier by a neutral vacancy are calculated.

A quantum antenna consisting of a set of two-level atoms situated on one straight line and prepared in different initial states is investigated. It is shown that if the initial state of a quantum antenna is a symmetric Dicke state, then for it a total suppression of radiation in definite directions is possible. Probability of simultaneous photon detections in these directions is equal to zero. This result is impossible for the pseudoclassical symmetric initial state of the antenna, which does not have quantum entanglement, and for such a state the probability of detecting a photon at any angle is always nonzero. The qualitative difference of the interference mechanism for the pseudo-classical and quantum antenna states is described.

Using the density functional theory method in the approximation of M062x/6-311+G(d,p), the calculation was performed of the optimal geometry and Raman spectra of metal aquacomplexes of periods II-IV [M(H₂O)₆]ⁿ⁺ (Mⁿ⁺ = Na⁺ , Be²⁺ , Mg²⁺ , Al³⁺ , Ca²⁺ , Sc²⁺ , Ti³⁺ , V²⁺ , V³⁺ , Cr³⁺ , Mn²⁺ , Fe²⁺ , Fe³⁺ , Co²⁺ , Co³⁺ , Ni²⁺ , Cu²⁺ , Zn²⁺ , Ga³⁺ и Li⁺ (m = 4)). Correlation dependences of the frequency of the symmetric stretching vibration of the bond of a metal ion with water molecules and the thermodynamic functions of the formation of aquaions are proposed.

Using stationary luminescence and pulse fluorometry methods, spectral-kinetic and photophysical properties of 9 methyl-10-hydroxi acridine(1,8)dione derivative dye (9,10-ACD) in polar (protonic and nonprotonic) solvents at 293 and 77 K have been investigated. For the first time, a new long-wavelength fluorescence band (LF, 670–710 nm) in polar protonic (methanol, ethanol) and nonprotonic (N,N-dimethylformamide, dimethylsulfoxide) at room temperature was revealed. This band has been formed from the high lying (in the range of 460–490 nm) singlet excited state responsible for the short-wavelength fluorescence band (SF). The LF is not revealed in low polar (methylene chloride), polar nonprotonic (acetonitrile) and high viscose protonic (glycerol) solvents at 293 K, as well as at 77 K in ethanol. It arises as a result of deprotonation of a molecule in an excited state and emission of the resulting anion in the long-wavelength region. Based on the analysis of the spectral and kinetic data of the SF decay and the LF rise, a mechanism for the dye anion formation depending on the basicity of the polar solvent is proposed. Possible practical applications of the revealed spectral effect in biology, medicine and analytical chemistry are proposed.

A generalized diffusion model of rotational depolarization of luminescence of polyatomic molecules with internal rotators is developed under the assumption of independent collision statistics for internal rotations and rotation of the molecules as a whole. The model is used to calculate the collisional depolarization of non-rigid oligonucleotides with fluorescent labels that are in the free state in solutions and in complex with nanoparticles. The changes in the fluorescence anisotropy during relaxation are analyzed depending on the ratio of the inertia moments of the moving parts of the molecule and the transition moments orientation. The conditions for possible enhancement of anisotropy and control of changes in the structure of biomolecules during their immobilization on the surface of nanoparticles are evaluated.

The syntheses of 3-formyl-4-hydroxybenzoic acid-derived ligands from ethylenediamine, diethylenetriamine, and triethylenetetramine are described. These ligands can further form hetero-binuclear complexes with transition metal ions (M²⁺ = Zn²⁺ ; Fe²⁺ ; Ni²⁺ ; Mn²⁺ ) and lanthanide ions (Ln³⁺ = Nd³⁺ ; Er³⁺ ; Yb³⁺ ).  The spectroscopic properties were studied using near infrared (NIR) luminescence emission spectra, fluorescence lifetime, and quantum yield. These hetero-nuclear complexes exhibited the characteristic lanthanide near-infrared luminescence in the solid state through energy-transfer from the chromophore to lanthanide ions. The d-block emission bands of transition metal ions in the solid state overlapped with f-f absorption bands of Yb(III), Er(III), or Nd(III), sensitizing the near-infrared luminescence of these hetero-binuclear complexes.

Detailed measurements of nonlinear optical properties and optical limiting for four phthalocyanine (Pc) derivatives (PcCo, PcCu, PcMn, and PcSi) are reported. The nonlinear optical properties were investigated using a Z-scan technique with a continuous-wave argon ion laser at 488 and 514.5 nm, and with a 532-nm pulsed Nd:YAG laser. All Pcs exhibited strong nonlinear properties and low optical-limiting thresholds. The nonlinear absorption coefficient, the sign and magnitude of the nonlinear refractive index, and the thirdorder nonlinear susceptibilities of each compound were calculated. Refractive nonlinear effects are the most dominant for continuous laser excitation and are mainly attributed to thermal effects, whereas the reverse saturation absorption coefficient may have an electronic origin. Threshold values indicated that the Pc derivatives are promising materials for optical-limiting applications.

The possibility of using the conversion of phthalates to fluorescein by preliminary hydrolysis of phthalates to phthalic acid followed by its dehydration into phthalic anhydride and the interaction of latter with resorcinol in analytical luminescence spectroscopy for the phthalates detection was considered. The formation of luminescent by-products of the auto-condensation reaction of resorcinol molecules supposedly with own oxidation and decomposition products was revealed. The luminescence spectrum of a by-products mixture of resorcinol transformation is overlapped with the spectrum of fluorescein and the relative quantum yield of mixture luminescence was 25%. This fact obstructs the use of this reaction for analytical purposes, since it requires special care in the sample preparation procedure and selection of reaction conditions to minimize or eliminate the formation of luminescent by-products.

It is shown that an analogue of single-pulse echo signal (edge magnetic echo) arises when an additional magnetic videopulse and the trailing edge of a sufficiently long radio-frequency pulse are simultaneously applied to the nuclear spin system in the domain walls of cobalt. It is formed by the mechanism of distortion of the leading edge of the effective radio-frequency pulse when the domain walls are displaced under the influence of a magnetic videopulse. This distortion occurs when the amplitude of the magnetic videopulse exceeds the threshold value leading to the onset of the displacement of domain walls, and is caused by the anisotropy of the local hyperfine field on the nuclei of domain walls. The role of displacements of domain walls in the formation of single-pulse echo signals in cobalt has been experimentally established. This also makes it possible to estimate the characteristics of the centers of domain wall fixing (pinning centers) by this method. The estimation coincides with the characteristics of domain wall pinning centers, determined by the effect of a magnetic videopulse on the two-pulse echo signal.

Multivariate models were developed on the base of raw low-resolution LIBS spectra of reference samples of low-alloyed steels for calibration of the concentrations of six chemical elements (C, Mn, Si, Cr, Ni, and Cu), which are the main technological and alloying additives. The multivariate models for C (RMSE=0.06% for test dataset) and Mn (0.12%) content are quantitative with an accuracy sufficient for practical application, semi-quantitative for Si (0.09%) and Ni (0.07%), and qualitative for Cr (0.13%) and Cu (0.08%).

The results of ellipsometric, X-ray, and spectral studies of In₂O₃ films deposited by dc-magnetron sputtering on Al₂O₃ (012) substrates are presented. The experimental data are interpreted in terms of the three-layer model of the film. As a result, it is assumed that large particles of the material are formed on the substrate surface at the beginning of the deposition process, and then the size of the crystallites decreases and they fill the gaps between the larger particles. After that, the film formation goes into the stationary mode. The presence of a transition layer with a band-gap of 1.39 eV, refractive index of about 3, and thickness of 25 nm is shown at the interface between film and substrate. The properties of this layer do not depend on the deposition time.

Using glucose as a reducing agent, a hydroxyapatite-silver (HA)Ag nanocomposite is synthesized, in which one silver nanoparticle is bound to each HA particle. The structural and optical properties of the nanocomposite are investigated. The technique of formation of plasmonic films (HA)Ag on the glass substrates surface is optimized. The role of modification of a glass surface with polyethyleneimine in the formation of homogeneous plasmonic coatings is demonstrated. The surface-enhanced Raman spectra (SERS) of the cationic porphyrin CuTMpyP4 adsorbed on the surface of the (HA)Ag film are measured. The detection limit of CuTMpyP4 is established as 10^-12 M, which is comparable to the sensitivity of the wellknown solid-state SERS-active substrate.

The main physiological and biochemical characteristics as well as the elemental composition of the lichens Xanthoria parietina (L.) Th. Fr., Parmelia sulcata Taylor, Hypogymnia physodes (L.) Nyl, and Hypogymnia tubulosa (Schaer.) Hav.) growing under conditions of insignificant anthropogenic load in one habitat were studied using different methods of optical spectroscopy analysis. The first three species are often used as indicators in the biomonitoring based on spectral analysis data. The content of chlorophylls a and b, total nitrogen (TN), phenolic compounds (TPC), antiradical activity (ARA) was determined by spectrophotometric method, and the phaeophytinization quotient (PQ) was calculated. The revealed values of physiological and biochemical parameters in all four species indicate the correspondence of their habitat to the background area. The physiological characteristics of the studied species are coordinated and interconnected to varying degrees. Twenty-two elements in lichen thalli were revealed using ICP-AES spectroscopy. These include macro- and microelements, as well as heavy metals and metalloids (HM). The maximum differences in metal content were found in X. parietina and H. tubulosa. Analysis of the mutual conjugation of the physiological, biochemical characteristics, elemental composition, and metal content made it possible to identify complex systems of correlations in each species. Differences in their structure may be associated with the specificity of the composition of secondary metabolites, which determine the features of adaptive reactions and the degree of tolerance of species. The implementation of a complex analysis of the physiological and biochemical characteristics as well as the elemental composition using various spectral methods is important for the development of the bioindication and ecological physiology of lichens.

The mechanisms of action of toxic organic compounds (OС) (pentane, hexane, benzene, o-xylene, butyl acetate, and benzopyrene) on the reed fescue Festuca arundinacea Schreb., which is a common plant in the urban environment, were studied applying amplitude-pulse modulated fluorometry (PAM). To that end, the photochemical activity of photosystem II (PS II) was evaluated using the parameters of the kinetic curve of chlorophyll a (Chl a) fluorescence induction in vivo. A dose- and time-dependent reduction in the content of hydrophobic membrane-bound chlorophyll pigments was found along with simultaneous accumulation of chlorophyllide (Chldе), a phytol-free product of chlorophyll degradation, in the leaves. It was shown that the effective quantum yield of photochemical reactions of PS II (Y(II)) decreased mainly at high doses of toxic compounds, wherein the level of photochemical quenching of fluorescence (qP) did not change significantly. We found that the coefficient of non-photochemical quenching (qN) significantly increased to different degrees, depending on the type of the toxicant and time of its exposure. A high negative correlation was observed between changes in qN, which characterizes the thermal dissipation of the absorbed energy, and the content of membrane-bound phytol chlorophyll pigments and carotenoids. On the other hand, changes in qN positively correlated with the content of Chldе formed during the OC processing. It leads us to the conclusion that the thermal dissipation of the absorbed energy as a result of the action of OC is proportional to the degree of destruction of the pigment apparatus of chloroplasts. This is confirmed by a positive correlation between the value of qN and the content of Chldе possessing a photodynamic effect. Thus, the qN parameter can serve as a reliable test for the damaging effect of various toxic technogenic factors.

We cоmpared the efficiency of some multivariate methods of recognition of drug classes in primary packages using THz transmission spectra. The advantages of the support vector machine are demonstrated with a classification error not exceededing 5.7% for two groups of analgetic drugs with a high level of heterogeneity of the samples in these groups.

It is established numerically that when active-pulse vision system registers signals from a diffusely reflecting underlying surface along inclined lines of sight, it is possible to select an area of small delay distances limited by the value L_zad-gr, where the spatial-energy profile of the recorded signal has the form of convex asymmetric curve with a maximum shifted to the beginning of the visibility zone. The value of L_zad-gr depends on the duration of the illumination and strobing pulses. For a co-operated object (equipped with retroreflectors), L_zad-gr coincides with the value previously set for horizontal observation lines. The width of the visibility zone for the cooperative and diffuse objects increases with the increase in the delay distance, tending to a certain limit value, depending on the duration of the illumination and strobing pulses. When observing on inclined lines of sight, the visibility angle in the vertical plane is determined by the duration of the illumination and strobing pulses, as well as the delay distance and the height of the vision system installation.

A method is proposed to assess the quality of Bessel light beams of higher orders (BLB_n, order n> 0) by analyzing digital computer images of two-dimensional transverse intensity distributions. One image is sufficient to assess the quality in a specific cross-section of the BLB_n. Algorithms are described that ensure the correct implementation of this technique, namely, the algorithm for the annular beam axis position estimation based on cluster analysis, the algorithm of the estimation of the initial approximation of the cane parameter when approximating the experimental diametral intensity distributions by the square of the Bessel function based on the analysis of the spectral power density of diametral intensity distribution. The proposed method and algorithms are implemented as an extension for the software package for analyzing the quality of Bessel light beams. Using a software package, the technique was experimentally tested on the example of analyzing the quality of BLB1 formed using KTP (KTiOPO₄) and KGW (KGd(WO₄)₂) crystals from the radiation of a semiconductor laser module (SCLM) and helium-neon laser (HNL). It is shown that the beam formed from the HNL retains the constancy of the radius along different azimuthal directions and conformity of the shape to the ideal BLB1 at a larger distance from the axicon than the SCLM, but at the same time it loses the constancy of the intensity along different azimuthal directions in the first ring more quickly.

We studied the diffraction of light on reflection holographic gratings in a layer placed between the coating and the substrate with refractive indices different from the average refractive index of the layer. The significant differences between the reflection and transmission coefficients of the light diffracted on such a holographic grating with a change in the amplitude of the modulation of the refractive index of the layer, and the reflection and transmission coefficients of reflection gratings in matched structures are established. It is shown that at large widths of the layer with a reflection holographic grating a significant rotation of the polarization plane of the reflected and transmitted diffracted waves takes place when the modulation amplitude of the layer changes. It is due to the Fresnel reflection of light at the boundaries of the layer.

Laser-induced breakdown spectroscopy (LIBS) based stand-off distance analysis of the calcium concentration in bulk liquid under high-pressure condition is carried out. The influence of salinity during the determination of the Ca concentration is studied. Machine learning classifiers are used in the estimation of the unknown Ca concentration in the liquid sample, for different experimental parameters or conditions. From the spectral information, the emission lines related to Ca II at 393 and 396 nm are visualized. Chlorine emission lines are not observed due to the requirement of high ionization energies. As the salinity (NaCl) of the sample solution is increased to 2500 ppm, the signal-to-noise ratio of the LIBS signal is improved by a factor of 0.85. The Ca II emission line peak intensity decreased with increase in ambient pressure conditions and stand-off collection distances. The opposite trend is observed with an increase in the laser fluence and the CaCl₂ × 2H₂O concentration in the sample solution. The Ca II 393 nm emission time period is estimated at (1/e)I₀ peak intensity. A typical Ca II 393 nm emission time period from 6.712 to 6.766 µs is observed. The specified value is obtained for a laser fluence of 9 J/cm², ambient pressure of 1 atm, stand-off collection distance of 0.6 m, 2500 ppm NaCl, and 1500 ppm CaCl₂ × 2H₂O. It is observed that the emission time period increased with increase in the CaCl2 × 2H2O concentration in the sample solution and laser fluences. The opposite trend is observed for an increase in the ambient pressure and stand-off distances. The results obtained from the spectral and temporal measurements are in correlation with each other. The best system model's performance metrics of 100% (Accuracy = Precision = Recall = F1-Score) are obtained under the fixed experimental conditions using the k-nearest neighbor classifier. 

It is shown that relations for the determination of pure electronic transition from diffuse absorption and emission spectra, obtained when assuming the microreversity of vibronic transitions, also derive from the quantum fluctuation theorem.

With the aim of improving the up-conversion luminescence intensity of high concentration Yb3+ /Er3+ doped microparticles, Yb³⁺ /Er³⁺ doped β-NaYF₄/β-NaLuF₄/β-NaYbF₄samples were prepared by the hydrothermal method. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to characterize the crystal structure and morphology. Intense blue emission (² H_{11/2 →} ⁴ I_15/2, ⁴ S_{3/2 →} ⁴ I^15/2) and red emission (⁴ F_{9/2 →} ⁴ I_15/2) of Er³⁺  were observed under 980 nm excitation. When the doping concentrations of Yb³⁺  and Er³⁺  were high, the up-conversion luminescence intensity using b-NaYbF4 as the host matrix was enhanced, and in the experiment the sample NaYbF₄:16 mol.% Yb³+ /32 mol% Er³+ with b- NaYbF₄ as the host matrix has the strongest luminescence.

Zn₂GeO₄ (ZGO) phosphor and Mn-doped ZGO (ZGO:Mn²⁺) phosphor were successfully synthesized through co-precipitation. Results indicated that Zn ions were successfully replaced by Mn ions, and Mn doping led to a lattice contraction. Under UV light excitation, the undoped ZGO exhibited a strong white-bluish emission at 517 nm and weak green emission at 530 nm, both of which were attributed to the native defects in the ZGO host. The near infrared emission (~740 nm) was attributed to the transfer of energy from nonbridging oxygen-hole centers to zinc (Zn_i) and oxygen-vacant state (V_О) in the ZGO host. ZGO:Mn²⁺ emitted a band at ~535 nm which originated from the ⁴ T₁–⁶ A₁ transition of Mn²⁺ ion. These initial findings showed that the luminescence properties in the green and near infrared range of ZGO phosphor can be controlled.

Glasses coated with different thin film layers exhibit different optical properties. Thus, ZnO thin films with Sn and Cr admixture (ZCTO) were deposited on the glass substrate surface by radio frequency magnetron sputtering. Picosecond laser-induced breakdown spectroscopy (ps-LIBS) was applied to achieve the rapid analysis of the doping elements in the ZCTO thin film. In addition, the transmittance spectra of the glasses coated with ZCTO thin films deposited at different sputtering times were recorded with the UV-VISNIR spectrophotometer. A red shift of 45±2 nm was observed in the absorption edge of the transmittance curve (UV wave band from 330 to 400 nm), which was highlighted with increase in the sputtering time. Moreover, the optical band gaps of ZCTO thin films were determined, which overall were larger than those of ZnO thin films only. Lastly, the relationships between the LIBS analysis and the optical properties of the glass samples were established. As revealed from the results, ps-LIBS can control or assist in the fabrication of high performance ZCTO thin films employed for glass production.

Self-reversed sodium D lines in laser-induced plasmas generated from soil samples with a sodium trace concentration of 42.3 ppm was examined using laser-induced breakdown spectroscopy (LIBS). The inverse pulse-energy dependence as well as spatially resolved behaviors of self-reversal were investigated using a pulsed Nd:YAG laser (532 nm, 7 ns) and a spectrograph with an ICCD camera. As pulse energy increases, the degree of self-reversal first augments then rapidly diminishes. The mechanism behind this lies in the separation of emission and absorption centers in wavelength, coupled with the fact that the central and outer layers of the plasmas were heated up equally with higher pulse energies. This indicates the possibility of avoiding self-reversal in an active manner.

The distinctive glow features of low-temperature RF CH₄/Ar plasma chemical vapor deposition and its correlation with plasma-deposited film characterizations were investigated. The optical emission spectroscopy diagnosis data and deposition results clearly indicated that, during CH₄/Ar glow discharge, the CH and C₂ species resulted from the low-energy electron-impact dissociation of CH₄ molecules that formed the deposition species, but the strong Ar emission lines were related to non-deposition species such as the argon atom. The results of the optical emission analysis indicated that the possible contribution of atmospheric pressure plasma-deposited film growth occurs primarily owing to a combination of electron-impactdissociation and ionization.

Four simple, low-cost, sensitive, accurate, and direct spectrophotometric methods for Risedronate sodium (RIS) estimation have been developed. All methods were based on pyridinyl sensitivity for the UV light at 262 nm. The proposed methods were extensively validated according to the ICH guidelines and proved as following Beer's law over the concentration ranges 6–120, 5–100, 17–170, and 15–150 µg/ml for methods 1, 2, 3, and 4, respectively. All the proposed methods were found to be precise with RSD values less than 2% and accurate with recovery values between 90–110%. These methods can fully fill the needs of QC routine tests plus meet different demands for Research and Development departments.

Chloramphenicol (CHL), dexamethasone sodium phosphate (DSP), and tetrahydrozoline HCl (THZ) are co-formulated for conjunctivitis treatment. The ternary mixture could not be simultaneously determined because of the overlap of the zero order absorption spectra. Herein, simple and validated UV spectrophotometric techniques have been developed for the determination of CHL, DSP, and THZ in their pure and ophthalmic dosage forms. Meanwhile, only CHL was directly determined at 284.0 nm in the range 4.0–36.0 µg/mL, while DSP and THZ were determined using single or double divisor derivative ratio spectrophotometric methods. For the single divisor derivative ratio-zero crossing spectrophotometric method (SDDR-ZC), 4.0 µg/mL CHL was used as a single divisor, where DSP and THZ were detected at 272.0 and 239.0 nm, respectively. Both DSP and THZ showed linearity ranges of 4.0–32.0 µg/mL for DSP and 3.0–24.0 µg/mL for THZ, whereas for the double divisor derivative ratio spectrophotometric method (DD-DR), (12.0 µg/mL CHL and 12.0 µg/mL THZ) and (12.0 µg/mL CHL and 12.0 µg/mL DSP) were used as double divisors for the quantitative assessment of DSP and THZ, respectively. Both DSP and THZ showed a linearity range of 4.0–32.0 µg/mL, and they were detected at 258.0 and 237.0 nm, respectively. The developed techniques were successfully applied for the determination of the three drugs in their dosage form. The proposed techniques were validated showing no significant differences when statistically compared to a reported HPLC method.

A rapid, sensitive, cost effective and reproducible first-order derivative spectrophotometric method was developed for the estimation of gefitinib in bulk and in its marketed formulation. Preliminary spectrophotometric determination of the drug was carried out in acetate buffer pH 2.8 and in 0.1 N HCl with a total of 20 parametric variations. The selected method with three parametric variations employing peak-zero (P-0) and peak-peak (P-P) techniques was assessed for stability indicating potential in force degraded solutions. The developed method was validated with respect to linearity, accuracy, precision, and robustness. Linearity was observed in the concentration range of 5–50 μg/ml with an excellent correlation coefficient (r² ) of 0.999. The limits of assay detection values were found for the range from 1.69–3.75 μg/ml, and quantitation limits ranged from 5.11–12.71 μg/ml for the proposed method. The proposed method was applicable for the determination of the drug in its marketed tablet formulation, and percentage recovery was found for the range from 97.42 to 98.58%.

A new, accurate, sensitive, and reliable kinetic spectrophotometric method for the determination of vitamin B₁₂ in biological samples and pharmaceutical formulations has been developed. A central composite design (CCD) of the response surface methodology was used in our research to investigate the effect of reaction time and temperature and the concentration of reagents including orange G, bromate, and sulfuric acid on the assay of vitamin B₁₂. Vitamin B₁₂ shows a strong inhibitory effect on the oxidation of orange G by bromate in acidic media. The wide linear dynamic range, low detection limit, and short time analysis introduce the proposed method as a new strategy for the determination of vitamin B₁₂ in biological and pharmaceutical samples. Also, linear polynomial mathematical models were obtained for the determination of vitamin B₁₂. Under optimum experimental conditions, the calibration curve was linear over the range 1.0–200.0 µg/mL. The limit of detection was 0.56 µg/mL. Statistical comparison of the results with the reference methods shows excellent agreement and indicates no significant difference in accuracy and precision.