Temperature effects on the initial transmission of the laser passive Q-switch based on the BDN dye-doped polyurethane matrix were investigated in wide temperature range from –60 to +60°C. The temperature behavior of the Q-switch initial transmission was analyzed since its characteristics determined significantly the parameters of laser generation. The measured output energy of a single pulse from the neodymium laser on the 4F3/2 → 4I11/2 transition was shown to be dependent on the mutual spectral location of the laser generation wavelength and the dye absorption band of the S0 → S1 electron transition.

New approach to the interpretation of the multiplet structure in the Shpol'skii spectra based on the symmetry consideration of the impurity molecule and crystal matrix is proposed. The reasons and peculiarities of doublet structure formation in the spectra of molecules without inversion center and highly symmetric molecules are considered. It is shown that the structure of electron density distribution in the naphthalene molecule causes a doubly degenerate of the electronic level of its ground state. The calculated data are compared with the experimental results. The main research stages and directions in the field of narrow-line spectroscopy of organic molecules are marked.

The 4-pentyl-4′-cyanobiphenyl (5CB) molecule conformation and structure alignment have been investigated by means of temperature variable Fourier transform infrared (FTIR) and photoluminescence (PL) spectroscopy in a wide temperature range (from −90 to 50 °C) covering the 5CB glass-like, metastable and stable crystalline, nematic and isotropic phases defined by differential scanning calorimetry measurements. The corresponding FTIR absorption and PL emission bands reflect a strong dipolar association and a formation of at least two types of 5CB dimeric structures with antiparallel or parallel orientation in the planar configuration. No formation of hydrogen bonds between the cyano groups and hydrogen atoms of the adjacent benzene ring has been found. Besides, a small amount of the 5CB monomer structure has been shown to be present in all phases. The observed temperature-induced changes in the IR and PL spectra can be used as an independent source of experimental information on conformational equilibria and structure alignment of 5CB in different states under the phase transitions.

The results of experimental investigations on the low-temperature fluorescence and absorption spectra of the 1- and 2-fluoronaphthalene impurities in the crystalline naphthalene are presented and analyzed. When the 1- and 2-fluoronaphthalene concentrations are less than 1%, the absorption and fluorescence spectra are shown to be composed of two identical band series, induced by the formation of two different centers, consisting of the single impurity molecules. The impurity concentration increase of over 1% results in the appearance of the additional structure in the polarized absorption spectra near the 0-0 bands of the single centers in a form of narrow bands with similar intensity and different polarization. This structure is associated with a formation of impurity paired centers, consisting of the two resonantly interacting molecules of either 1-fluoronaphthalene, or 2-fluoronaphthalene. Besides, in the case of the 2-fluoronaphthalene, the absorption spectra contain intense peaks, located ∼ 45 cm−1 higher in frequency, relative to the 0−0 transition bands for each single-center, and consisted of complexes of narrow lines. These spectral peaks are also explained by a formation of impurity paired centers, but here interactions between the molecules are not resonant. For the pure naphthalene crystal factors, causing the observation of additional oppositely polarized weak bands in the absorption spectra at ∼ 10 cm−1 near the Davydov doublet components, are described.

Abstract Fluorescence and absorption spectra of the 2-fluoronaphthalene admixtures in naphthalene were studied at low temperature (T = 4.2 К). Two types of pairwise impurity centers were formed at admixture concentrations of more than 1 wt%. Polarization of absorption bands was detected; these spectra were determined by resonance interactions between molecules of the impurity center. Resonant splitting of electronic levels for the translationally nonequivalent molecules in the unit cell of the naphthalene crystal was analyzed for the case, when one molecule was in the similar phase with the incident light wave and the other one was in antiphase.

The effects of the 5CB liquid crystal (LC) cooling regimes on its luminescence spectra at the low temperature (T=4.2 K) have been found out and investigated. Experiments have been carried out at two cooling rates: 2 and 150deg/min. Differential scanning calorimetry (DSC) data allow us to establish that the 5CB glass-like state (GLS) is formed during the rapid cooling of the sample. Peculiarities of the LC dimer formation under the different cooling conditions are discussed.

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 TiO 2 (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.

We have studied the influence of inorganic particles on the photoluminescent properties of the nematic liquid crystal 5CB in composites based on carbon nanotubes (CNTs) and hybrid nanoparticles consisting of carbon nanotubes and platelets of the organically modified mineral montmorillonite (MMT). We show that the photoluminescence (PL) of 5CB + CNT composites is characterized by excimer emission of the 5CB molecules. Adding carbon nanotubes to the liquid crystal medium leads to a considerable decrease in the photoluminescence intensity, but has practically no effect on the bulk structural alignment in the organic matrix. Hybrid CNT–MMT particles form a uniform coagulation network in the composite with 5CB and significantly disrupt the nematic structure of the liquid crystal. Bent conformations of the 5CB molecules appear which are typical of the liquid crystal monomers. The presence of the indicated 5CB conformers in the system and also the weaker interaction between the liquid crystal and the inorganic filler explain the increase in the photoluminescence intensity for the composite 5CB + CNT–MMT compared with the emission characteristics for the original liquid crystal.

The luminescence spectral characteristics of nanocomposites based on the 5CB liquid crystal with dispersions of inorganic particles of carbon nanotubes (CNTs), the mineral montmorillonite (MMT), and nanotubes of titanium dioxide TiO2 (TNT) were investigated in the temperature range of 4.3–300 K. The IR absorption spectra of the composites at room temperature in the region of 390–4000 cm−1 were studied. The dependence of the luminescent properties of the composites on the physical properties and parameters of the nanoparticles was studied. It was established that the longwave shift of the luminescence spectra of the composites in relation to the spectra of the pure liquid crystal is related to the specific surface area of the nanoparticles. The longwave shifts of the spectra at room and low temperatures are analyzed.

The characteristics of interphase interactions in heterocomposites based on 5CB liquid crystal are investigated by infrared spectroscopy. Organomodified natural montmorillonite (OMMT) aluminosilicates from three geological deposits and OMMT-CNT (carbon nanotubes) hybrid particles are used as filler materials. Cetyltrimethylammonium bromide (CTAB) is employed as a surface modifier. Interphase (van-der-Waals) interactions are found to occur at the phase boundaries of these heterocomposites, with the strength of the interaction dependent on the type of MMT. Spectra of the hybrid nanoparticle powders show that CNTs have an effect on the conformation of the CTA(+) modifier alkyl chains, the degree of which also depends on the form of MMT. Of the systems with OMMT, the composite with strongest interphase interactions was found to have the largest amount of electro-optical memory and the highest optical transmission. The presence of hybrid OMMT-CNT particles in these systems leads to the disappearance of the memory effect, a decrease in optical transmission, and a significant drop in the electrical breakdown voltage of the material. The effect of the CNTs is greatest in systems with the strongest affinity among the components of the composite.

For the first time, the luminescence spectra of two polymorphic forms of phenyl salicylate (salol) have been obtained. Both spectra show the vibronic structure. The average spacing between vibronic components is 1250 cm–1. Based on the infrared spectroscopy study, it is concluded that the interval between vibronic components in the luminescence spectra corresponds to the ν(C–OH) stretching vibration. The luminescence spectrum of the metastable phase is shifted by 760 cm–1 to the low-frequency side and is much wider relative to that in the stable phase. The presence of an OH group in the orto-position on the substituted ring results in the asymmetry of a molecule and the localization of an electronic excitation on this ring.

The microstructure and electrical conductivity of 4-pentyl-4'-cyanobiphenyl (5CB) liquid crystal (LC) filled with multiwalled carbon nanotubes (NTs), organophilic montmorillonite (OM) clay platelets or their hybrid mixture OMNT were studied in the temperature range 290-350 K. The OMs were prepared by organic modification of montmorillonites obtained from different mineral deposits. In general, the samples 5CB+OMNT containing OM demonstrated more homogeneous distribution of filler particles than the samples 5CB+NT with the same amount of nanotubes. For the OM based on montmorillonite from Pyzhevsk deposit (Ukraine) we obtained that change of OMNT filler concentration from 1 to 4.5 wt% resulted in transition from the well developed nanoparticle network to the structure of isolated agglomerates. This was accompanied by an increase (1% of OMNT filler) and a decrease (4.5% of OMNT filler) of electrical conductivity in more than one order of magnitude as compared with the 5CB+NT composite with the same amount of nanotubes. The microstructure and electrical conductivity of the composites were also dependent on the geological origin of the clay minerals.

A method to modify a montmorillonite (MMT) clay mineral (CM) surface by surfactant (SA) cations with simultaneous doping by multiwall carbon nanotubes (MWNT) has been proposed. The structure and spectroscopic properties of composites based on MMT from two deposits (Cherkassy and Pyzhevsk, Ukraine) that differ in the inorganic impurity contents and cation-exchange capacities (CEC) have been investigated. Cetyltrimethylammonium bromide (CTAB) was used as the SA. According to x-ray diffraction analysis, CTA+ cations intercalated into MMT interplanar spaces expand them significantly whereas MWNTs do not affect the MMT galleries due to the much larger sizes of the former. Studies of the composite materials by IR spectroscopy revealed the mutual influence of the components appearing as the ordering of near-surface layers in the aluminosilicate framework and a change in the modifier methylene chain conformation at the interphase boundary. The majority of CTAB (~90%) is shown to be located inside the MMT galleries, the packing arrangement of which depends on the CEC value and affects the interplanar distances in MMT. The alkyl chains of the CTA+ cations on the outer surface of the MMT plates are sorbed by nanotubes, thus providing contact between the organoclay and MWNT surfaces.

Photoluminescence (PL) of a heterocomposite, consisting of the nematic liquid crystal (LC) 4-pentyl-4'-cyanobiphenyl (5CB) and anisometric nanoparticles of montmorillonite (MMT) clay, modified by cetyltrimethylammonium bromide (CTAB) has been investigated at 4.2 and 300 K. The incorporation of this organoclay (B4) to 5CB decreases the emission intensity by 7-8 times due to efficient resonant quenching of the exciting energy by the organoclay. The spectrum shifts to a long-wave region, with this effect being considerably larger at low temperatures. Graphical separation of complex bands, corresponding to the bulk 5CB and 5CB + B4 heterosystem at both temperatures revealed that the presence of the organoclay resulted in a significant growth of LC dimer quantity, shifting spectra towards longer wavelengths. Changes in the 5CB luminescence under organoclay influence can be explained by quite strong interphase interactions specified earlier by infrared spectroscopy between the MMT surface and LC, and by a realisation of more flat conformations of 5CB molecules. Confinement effects prevent full crystallisation of 5CB in the 5CB + B4 composite, and LC dimer structures located in the organoclay near-surface layers on the outer surface of the nanoparticles and inside its galleries remain in a larger amount, at low temperature, when compared to bulk 5CB. The remaining LC crystallises and photoluminescence from the 5CB monomers becomes intense.

The structure and photoluminescent properties of natural montmorillonite (MMT) aluminosilicates from three mineral deposits that were modified by cations of sodium or the surfactant cetyltrimethylammonium bromide (CTAB) have been investigated. X-ray fluorescence analysis showed significant differences in the concentrations of the inorganic dopants in these materials. An x-ray diffraction analysis established that incorporation of the CTA+ long-chain cations into the MMTs expands remarkably the mineral interplanar distances, the values of which are close to each other for all organoclay samples under study and equal to 1.8–2.0 nm. The photoluminescent properties of the Na-form of the MMTs are shown to depend on the amount of introduced dopant capable of either enhancing or quenching the emission. Deposition of CTAB on the mineral surface influences the luminescence pattern, the spectral contour and wavelength range being practically the same for all modified samples. The emission may intensify or weaken because of such surface modification.

The luminescent and optical characteristics of ZnS thin films produced by close-spaced vacuum sublimation technique (CSVS) were investigated in this work. Luminescent and optical investigations allowed determining the fluorescence centers of native defects and uncontrolled impurities.

The effects of the modification of natural layered montmorillonite (MMT) clay by cetyltrimethylammonium bromide (CTAB) cations on the structure and optical properties of the composite material based on this mineral (4.5%mass) and a nematic liquid crystal (LC), 4-pentyl-4'-cyanobiphenyl (5CB), have been investigated. As shown by small-angle X-ray diffraction and infrared (IR) spectroscopy experiments, this modification results in a significant expansion of the interplane spaces in the MMT nanoparticles and a considerable growth of their surface affinity to the 5CB molecules, which allows the LC molecules to penetrate into the MMT galleries and additionally expand these galleries. According to IR studies, this heterosystem possesses van der Waals interactions between its components on the phase separation boundary and, as a result, orientation alignment of the molecules in the near-surface layers occurs. These interactions specify the electro-optical properties of the composite. When an electric field is applied to a system, the light transmittance of the material increases due to the induced orientation of the LC dimers. This LC ordering remains even after the voltage is shut off, i.e. the system shows an electro-optical memory effect.

Using the methods of luminescent and emission spectroscopy analysis, the peculiarities of luminescent water from different sources were studied, and the concentrations of macro- and microelements in water samples were determined. Quantitative analysis of Antarctic samples of ice of different age was carried out and the existence of different chemical elements was studied. The influence of "hardening" factor on luminescence spectrum of Antarctic and distilled water was investigated.

Photorefractive material have certain prospects for usage in coherent-optical schemes of the optical signal processing. Their values in this aspect are non-linear resopnse to the intensity of signal and variety of temporal characteristics of record and erasure of images, including holographic ones. In this presentation, questions connected with usage of photorefractive crystals in the holographic correlator with the associative resopnse to fragments of recognized signal were investigated. Particularity of the correlator scheme consists in getting response in the manner of the signal under investigation itself. Due to it, the level of signal identification increases under its associative processing. Use of spatial modulator of signal wave front and photorefractive crystals in the scheme allows to vary a structure of angular spectrum of recorded images when writing the holograms. In certain limits, it gives a possibility to control sensitivity of image as to change of structure of fragments which restore a hologram, keeping stable associative response.