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Novel D–π–A–π–A′ chromophores with different substituents in the donor moiety were synthesized and NLO coefficients for composite polymer materials doped with them were measured.

A new methacrylic monomer, 3,5-bis[2-(N-ethylanilino)ethoxy]benzyl methacrylate (MBA), has been synthesized. Methacrylic copolymers with different content of bi-chromophore fragments in the side chain were obtained by radical copolymerization of methyl methacrylate and MBA, followed by azo-functionalization reaction. The composition of the obtained copolymers was established, and their thermal properties were determined. Thin films of synthesized copolymers were prepared by spin-coating and the nonlinear optical characteristics of the obtained materials were investigated.

YVO4:Yb,Er upconversion nanoparticles (UCNPs) are synthesized to study the possibility of using them as nanoprobes to solve biological problems. Aqueous colloidal solutions of UCNPs are injected into the bodies of grape snails. When preparations from animal organs are irradiated with a continuous wave (CW) laser at a wavelength of 980 nm, luminescence is observed in the region of 520–560 nm, due to radiative transitions in Er3+ ions. A comparative analysis of the behavioral activity of animals with injected nanoparticles and control animals with no nanoparticles reveals no signs of toxicity. The nanoparticles are promising as luminescence nanoprobes in biological problems.

Nanoparticles of YVO4 doped with Yb3+ and Er3+ ions, which exhibit upconversion luminescence upon cw laser excitation at 980 nm, are synthesized according to the familiar hydrothermal procedure. Physical and structural features of intermediate products obtained at different technological stages of creating upconversion nanoparticles are established via electron microscopy, Raman spectroscopy, and luminescence microscopy.

The results from a comparative analysis of the emission spectra of upconversion YVO4:Yb, Er nanoparticles synthesized in sizes ranging from 10 nm to 1 μm are used to discuss the contribution from high-energy oscillators on the surfaces of nanoparticles to the nonradiative energy transfer between Er3+ ion levels, and to the formation of the red emission band at 660 nm.

The purpose (objective) of the empirical study is the measurement of the accuracy of expert-proctors in detecting cheating in online testing. Sample of the study. 35 test takers passed an online test of general knowledge on the basis of 30 multiple choice questions. Half of the subjects (18 persons) were “artificial cheaters” — they used cheat sheets with correct answers. Methods. The video recording of the testing process included a “screen capture” so that expert-proctors could observe all cursor movements, see a recording of the subject’s facial expressions and a visual focus of attention in a separate window (recording from the front camera), and could listen to the subject pronouncing the task conditions and answers (“oral decision”). 14 experts took part in rating of video recordings, of which 8 experts showed satisfactory results in terms of the level of accuracy in detecting cheating (their accuracy that was measured using the Kappa coefficient was higher than 0.5). Conclusions. A high asymmetric validity of expert assessments is revealed. More accurate experts allowed a negligible (about 5 percent) number of errors of the “false alarm” type, but a relatively large number of errors of the “skip” type. Recommendations are made for the practical use of the expert assessment method in combination with automatic chronometric analysis of the degree of atypical protocols and subsequent control of face-to-face offline testing of all suspected subjects (examinees).

Using amplified femtosecond pulses at a wavelength of 1028 nm, the second harmonic is generated at a wavelength of 514 nm by composite polymer films containing D-π-A (push–pull) chromophores with quadratic optical nonlinearity. It is shown that these films are photostable with respect to laser pulses having peak intensities of up to 11.6 GW/cm2. The effective generation of the second harmonic is observed in a wide range of pump beam incidence angles (20°–80°) with a maximum in the vicinity of 60°.

Unlike standard nanodiamonds (NDs), boron-doped nanodiamonds (BNDs) have shown great potential in heating a local environment, such as tumor cells, when excited with NIR lasers (808 nm). This advantage makes BNDs of special interest for hyperthermia and thermoablation therapy. In this study, we demonstrate that the negatively charged color center (NV) in lightly boron-doped nanodiamonds (BNDs) can optically sense small temperature changes when heated with an 800 nm laser even though the correct charge state of the NV is not expected to be as stable in a boron-doped diamond. The reported BNDs can sense temperature changes over the biological temperature range with a sensitivity reaching 250 mK/√Hz. These results suggest that BNDs are promising dual-function bio-probes in hyperthermia or thermoablation therapy as well as other quantum sensing applications, including magnetic sensing.

YVO4:Yb,Er luminescent nanoparticles (NPs) with sizes of 10–700 nm are produced. The use of laser excitation wavelengths of 980 and 257 nm results in the emission of Er3+ ions in the spectral region of 527 and 555 nm. No spectral line of Er3+ ions is recorded at 660 nm, which is indirect evidence of the low efficiency of nonradiative multiphonon intra-ion transitions and the insensitivity of NPs to luminescence quenchers in an aqueous solution.

Spectroscopic data are presented for the motion of molecules in a liquid during double-pulse excitation and registration of the ultrafast optical Kerr effect (OKE). It is shown that selective spectroscopy of individual molecular motions can be achieved by choosing certain parameters of the double-pulse sequence.

The aim of the study was to obtain the data of stable oxygen isotope composition of Late Pleistocene and Holocene ice wedges of Mamontova Gora and Syrdakh exposures and their chronology, and reconstruction of winter air temperature during the time of ice wedge formation. Direct dating of organic microinclusions from the ice wedges of Mamontova Gora outcrops allowed to establish that the ice wedges are younger than 20 ka, but older than 10 ka BP. δ18O values of the Late Pleistocene ice wedges of Mamontova Gora vary from -24.7 to -30.9 ‰, δ18O values of the Holocene ice wedges of this exposures range from -23.2 to -25.9 ‰. δ18O values in the Late Pleistocene ice wedges near Syrdakh Lake vary from -29.2 to -32.5 ‰. Reconstructed mean winter air temperature during the most part of the ice wedge growth period in Mamontova Gora site within Late Pleistocene varied from -28 to - 31°C, mean January temperature reached -42, -46°C, for the Syrdakh Lake site Late Pleistocene winter conditions were more severe: mean winter air temperature varied from -30 to -32°C, mean January air temperature reached -44, -48°C. Holocene mean winter air temperature were higher and varied from -24 to - 28°C, mean January temperature varied from -36 to -42°C.

The signal of the ultrafast optical Kerr effect (OKE) in liquids, including toluene C7H8, nitrobenzene C6H5NO2, and acetonitrile C2H3N is analyzed. It is shown that considering the correlation between the orientational and librational responses allows us to determine the rise time of the orientational response associated with the inertial nature of molecular rotations over a time interval of 300–500 fs after the impact of a laser pulse, and to increase the accuracy of determining the form of the Raman spectral density function.

Experiments on recording the ultrafast optical Kerr effect (OKE) in solution of europium(III) β‑diketonate complexes in toluene at a concentration of 10–2 mol/L showed that the total OKE signal is not a superposition of two contributions, one of which is related to the vibrational–rotational dynamics of toluene molecules, while the other is due to the vibrational–rotational dynamics of the europium(III) complexes. This immediately indicates that the europium(III) complexes essentially change the structure of liquid toluene, which is reflected in the character of an orientational response in picosecond range.

The characteristic durations of energy exchange for Ce3+ impurity centers with lattices in a LiLuF4 crystal and the characteristic lifetime of free photoexcited charge carriers are determined in time-resolved experiments using a pump–probe scheme. The absorption saturation parameters of femtosecond laser pulses with a wavelength of 263 nm are characteristic of a slow absorber that participates in absorption from the excited state.

The decomposition of the recorded signal of the ultrafast optical Kerr effect (OKE) in benzonitrile into its components corresponding to different molecular contributions is considered. An optical scheme based on two-pulse nonresonant pumping with the registration of a test laser pulse is devised for this purpose.

Experiments are performed on registering induced changes in the refractive index of a cadmium sulfide single crystal with femtosecond time resolution in the transient lens and transient gratings geometries. The lifetime of photoexcited charge carriers (photocarriers) is estimated at 230 ps. An additional component, characterized by a decay time of units of picoseconds, is found in the efficiency decay of the transient grating of free carrier concentration. It is shown that this time is determined by the thermalization rate of photocarriers.

The article presents the results of long-term field studies of methane in the upper part of permafrost for the different geomorphological levels of Central Yakutia. Patterns of spatial distribution of methane content across different landscapes were found. The highest concentrations of methane are found in alas deposits, the major role of methane in the conservation there goes to the moment of freezing the thermokarst lake draining. The difference in methane content in the sediments of the Late Pleistocene Ice Complex on the left and the right bank of the river Lena was identified. That is likely caused by the conditions of ice complex formation.

Results from the nonresonance spectroscopy of CdS/CdSe quantum dots (composites of CdSe–CdS nanoparticles (core–shell)) are presented. The nonlinear optical properties of CdS/CdSe QDs in PMMA are studied with fs pulses at 1053 nm using the transient lens technique. QDs generate rapidly oscillating signals with amplitude rise times of around 200 fs and decay times of around 500 fs, while pure PMMA polymer only generates an oscillating signal whose envelope coincides with its autocorrelation function.

The quantum size effects of colloid water-organic media synthesized nanocomposites (CdSe–CdS core–shell) in toluene solution is studied. Femtosecond fluorescence up-conversion spectroscopy is used to establish that quantum dots are characterized by a biexponential decay of luminescence kinetics: the decay times are 1.8 and 26.8 ps for nanoparticles with average sizes of 2 nm and 4.5, and 68 ps for nanoparticles with an average size of 2.9 nm.

Novel D-π-A chromophores with quinoxaline/quinoxalinone core in the π-conjugated bridge and various bulky groups in the acceptor moiety have been synthesized and systematically investigated at molecular level by UV–Vis spectroscopy, DFT calculations, electrochemical and TGA-DSC methods as well as at materials level by the example of PMMA-based composite polymer materials doped with different chromophore contents using molecular modeling and SHG technique. Chromophores exhibit positive dioxane/chloroform solvatochromic shift of ca. 50 nm, high values of first hyperpolarizability and dipole moment, small energy gap and good thermal stability. Tolyl and cyclohexylphenyl substituents unlike phenyl can be treated as most effective isolating groups, preventing chromophore pronounced aggregation even at 30 wt% content. Femtosecond nonlinear optical (NLO) activity was studied for poled thin guest-host polymer films with various chromophore weight content. Film DBA-VQPhV-TCFPhCy(25 wt%)/PMMA with bulky cyclohexylphenyl groups in chromophore acceptor shows maximal NLO coefficient, d33, values among the studied materials (37 pm/V) as well as good long-term stability of NLO response together with excellent chromophore thermal stability (Td = 256 °C). Composite materials doped with quinoxaline chromophores are photostable with respect to laser pulses with peak intensities up to 11 GW/cm2.

The features of the integrated diagnostics of the discs of gas turbines of gas-compressor units using eddy-current and dye-penetrant testing are considered. The effectiveness of the detection of the crack-type defects in HPT and LPT discs under the first tooth of the fir-tree slots of the discs along the contact line of the teeth of the comb and blade butt are demonstrated. The calculations of the stress–strain state allowed the estimation of the occurrence of cracks in the fir-tree slots of discs, as well as the service life of discs up to crack formation at extraordinary operating temperatures. Integrated quality control by eddy-current and color capillary nondestructive testing provides reliable crack detection in details without serious costs for mechanical preparation of items for inspection along with a substantial reduction of the labor-intensiveness and depth of the inspection.

We have fabricated the upconversion nanoparticles (NPs), which are nanocrystallites of 10 nm, doped with Yb3+ and Er3+ ions, prepared through hydrothermal method. Monitoring of their photophysical properties had been realized at different fabrication stages by using electron microscopy and luminescence spectroscopy under photoexcitation of the NPs with the 100 mW laser at 980 nm wavelength. The performed monitoring allows us to observe dramatic changes in the upconversion properties of the NPs during the sequence of the fabrication stages and revealed very strong correlation between the NPs’ upconversion efficiency and their structural specificities.

Bulk SrTiO3 doped by 40 keV Cr+ ions and substrate temperature Timp = 600°C is studied. This sample exhibits supercontinuum generation by amplified femtosecond laser pulses (λ = 800 nm; repetition rate, 3 kHz; pulse duration, 150 fs; pulse energy 4 µJ), recorded by a monochromator with a PMT. The blue edges of the supercontinuum spectra differ, depending on the location of the focused laser beam spot on the sample.

The first experimental results on selective detection of the collective (libration) response in a liquid using a scheme of non-resonance double-pulse spectroscopy based on detecting the ultrafast optical Kerr effect (OKE) in ortho-dichlorobenzene at room temperature are presented. Nonrelevant vibrational and rotational responses are dumped and the relevant libration molecular responses are amplified by varying the duration, delay, and relative intensities of linearly polarized pump pulses.

We report on the decomposition of the molecular contribution to the optically heterodyne-detected optical Kerr effect (OHD-OKE) in benzonitrile C6H5CN in the process of double-pulse laser excitation. The pump pulses with linear orthogonal polarizations, controllable intensities and timing enable us to manipulate the amplitudes of various molecular responses due to the fact that the OHD-OKE signal is formed by the superposition of independent third-order responses associated with each pump pulse. We apply this technique to detect the intermolecular response selectively by using an excitation scenario with suppression of orientational and intramolecular responses. A detailed comparative analysis of third-order optical responses indicates strongly that the double-pulse excitation of the OHD-OKE is the useful spectroscopic technique to obtain precise information on the intermolecular spectrum in liquids.

Simultaneous control over the vibrational and rotational molecular responses in ultrafast optical Kerr-effect signals in acetonitrile, toluene, and chloroform at room temperature is achieved by means of non-resonance excitation with two 30-fs orthogonal linearly polarized laser pulses. It is shown that the orientational response of the molecules can be suppressed and their vibrational response isolated by enhanced the delay between the exciting pulses and their relative intensity.

The control of the coherent vibrational and rotational molecular motions in acetonitrile C2H3N was achieved by using the optically heterodyne-detected optical-Kerr-effect spectroscopy. A sequence of the two pump pulses with parallel and orthogonal polarizations was used for the non-resonant selective excitation of the molecular motions. The measurements showed that it is possible to control the molecular motions through the key parameters: the separation time, the relative intensities and polarization of the sequential pulses. The variation of the key parameters specifies the regimes of amplification and the suppression of the molecular responses. Two excitation scenarios with the amplification and suppression of the rotational responses were used as an example. The vibrational response was amplified in both cases.

We have studied picosecond dynamics of photo-induced charge carriers in CdSe/CdS nanoparticles with sizes of 2.0 and 2.9 nm in toluene colloidal solutions using femtosecond up-conversion spectroscopy. The kinetics of nanoparticles luminescence excited by laser pulses of 50 fs duration at 350 nm were observed. The simulation of experimental data showed that electron thermalization occurs within 0.5 ps, while recombination processes have characteristic times of 5 and 20 ns, although these cannot be unequivocally identified using the simplest recombination model with direct transitions and single type of traps. However, a comparative analysis indicates a fundamental difference in the mechanisms responsible for the dynamics of charge carriers in the time interval up to 5 ps after laser excitation, which we associate with different structures of traps in 2.0 and 2.9 nm particles.

We have synthesized YVO4: Yb, Er nanoparticles in the size range of 100-500 nm, which form aqueous colloidal solutions and are luminescent when excited by femtosecond light pulses at a wavelength of 263 nm. It was established that the luminescence occurs due to the emission of Er3+ ions in characteristic spectral lines at 525 nm and 550 nm. However, an effective quenching channel for metastable levels of Er3+ ions is evident, so that the characteristic luminescence line of Er3+ ions in the 660 nm region is absent. We associate this quenching channel with a large concentration of lattice defects with possible localization of high-frequency quenchers.

Experimental results on the electron relaxation time and diffusion coefficient in hydrogenated amorphous silicon films that exhibit intrinsic and electronic conductivity at room temperature are reported. It is found that, for these two types of films, the relaxation times are 1 ns and 465 ps and the diffusion coefficients are 0.54 and 0.83 cm2 s−1. It is established that, as the pulse intensity is increased, the decay time of the induced-grating signal shortens.

Two-pulse control of time-dependent anisotropy in liquid carbon tetrachloride at room temperature is implemented by using femtosecond polarisation spectroscopy. The liquid is excited by a train of two linearly polarised laser pulses, and the state of anisotropy is probed by a weak third pulse with registration of the optical Kerr effect. It is shown that by varying the delay between the exciting pulses and their relative intensity, selection of contributions of individual intramolecular modes into the recorded signal is achieved.

Optical control of coherent intramolecular oscillations in chloroform CHCl3 and dimethyl sulfoxide (CH3)2SO is attained experimentally under normal conditions by means of femtosecond polarization spectroscopy. Nonresonant excitation of the medium is accomplished by a sequence of two linearly polarized laser pulses. The state of the medium is probed by the third pulse via the optical Kerr effect. We show that control over the vibrational dynamics of molecules on a sub-picosecond scale can be achieved by varying the delay between the excitation pulses and their relative intensity.

The special features of diagnosing disks of gas turbines of gas-compressor units by the ultrasonic flaw detection method are considered. The efficiency of detecting crack-type defects in disks of HPT and LPT rotors under the first tooth of fir-tree slots of the disks in the area of trapezoidal grooves for tightening plates is shown. The application of the ultrasonic flaw detection method substantially increases the reliability of crack detection.

A novel molecular polarization spectroscopy method of processing the strengthened femtosecond signals, based on the ultrafast optical Kerr effect, is proposed. The processing of the reference chloroform signal by the novel method at a room temperature is demonstrated. It is shown that due to the manipulation by individual molecular motions through the constructive or destructive interference of corresponding wave packets it is possible to determine directly from the experiment such constants of molecular dynamics as the relaxation times of the coherent vibrations (≈1.5 ps) and orientation anisotropy (≈1.2 ps).

The femtosecond selective spectroscopy of vibrational-rotational dynamics of molecules in a liquid was realized using optical Kerr effect registration under two-pulse nonresonant excitation. The object chosen for the study was the chloroform at room temperature. It was shown that control of the separate molecular motions by creating the constructive or destructive interference of corresponding wave packets allows one to determine directly from the experiment such constants of molecular dynamics as the relaxation times of the coherent vibrations (≈1.5 ps) and those of orientational anisotropy (≈1.2 ps).