Synthesis of photochromic optically transparent polycarbonate glasses and study of their properties

Procedure was developed for surface dyeing of polycarbonate glass with photochromic thermally relaxing compounds from the classes of spiropyrans, spirooxazines, and chromenes via diffusion of photochromic molecules from solutions in cyclohexanone. It was shown that the highest diffusion efficiency of photochromic compounds without loss of the optical surface quality of polycarbonate glass is reached at a temperature of 80°C. Samples of photochromic polycarbonate glasses were obtained and their photochromic properties were studied.     

The structure ofO-arylmercury derivatives of dihydroxy-9,10-anthraquinones and their reactions with anions

The structure of mono- and di-O-arylmercury-derivatives of quinizarin (1,4-dihydroxy-9, 10-anthraquinone) and anthrarufin (1,5-dihydroxy-9, 10-anthraquinone) and their reactions with Br^–, Cl^–, OH^–, and^tBuO^– anions in the solid state and in aprotic solvents were examined by vibrational and electron spectroscopy. These reactions result in cleavage of the O-Hg bond. The formation of ions or contact ion pairs depends on the size and nature of the counterion; quinizarin dianions give very strong ion pairs with K⁺ cations, which do not cleave in DMSO. The electronic structure of mono- and dianions of the compounds studied is discussed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2933–2940, December, 1996.     

Stimulated Raman scattering in light and heavy water under picosecond laser excitation

The spectra of stimulated Raman scattering in ordinary and heavy water under excitation by second harmonic of a picosecond Nd:YAG laser were compared. It was shown that when stimulated Raman scattering is excited in water in cavities of a photonic crystal (synthetic opal matrix constructed of silica nanoglobules) or a photonic glass in the form of close-packed monodimensional millimeter-size amorphous-quartz balls, the efficiency of stimulated Raman scattering increases significantly compared to a uniform liquid medium.     

Stimulated infrared emission under excitation of condensed molecular dielectrics with giant pulses of a ruby laser

Stimulated infrared (IR) emission from a condensed dielectric medium under exposure to a giant pulse of a ruby laser is reported. This effect was predicted in the theoretical paper [1]. Experimental studies were carried out for a number of molecular liquids in two experimental geometries. In the first case (“in transmission” geometry) the propagation direction of the detected IR radiation coincided with that of the exciting radiation. In the second case IR radiation generated was detected in the opposite direction. The angle of divergence of IR radiation was found to be of 10⁻² rad, while the conversion efficiency with respect to the pumping intensity depended on the type of molecular liquid and varied in the range of 0.05–0.6%. Possible microscopic mechanisms of generation of IR radiation under pumping of the dielectric medium with visible or ultraviolet (UV) radiation are analyzed.     

Structure of fullerene-containing soot at different formation stages of arc discharge vaporization of graphite

Electron microscopy is used in a study of nanoclusters of the carbon soot deposited on a probe in different areas of arc discharge during graphite vaporization under conditions favorable for fullerene synthesis. It is found that the spatial network of soot nanoclusters consists of alternating regions of higher density or associates of carbon particles. Two types of nanoclusters have been identified with the correlation radii of the associates equal to 0.6–0.8 and 1.6–2.2 nm, respectively. Type I nanoclusters are dominant in the soot microparticles, and their structure shows practically no variations with increasing separation r of the soot collector from the discharge axis over the range of distances studied, r=1–9 cm. The effective radius R ₀ of the “elementary” particles making up the associates in the soot nanoclusters of Type I calculated with the use of scaling relationships is 0.15–0.17 nm and is close to the gas-kinetic radius of carbon atoms. Type II nanoclusters have been identified in soot collected at r>3 cm. Values of R ₀ calculated in this case are 0.6–0.9 nm and decrease with increasing r, which indicates the presence of fullerene molecules in these nanocluster associates.     

Generation of terahertz radiation in cubic non-centrosymmetric crystals

The conditions of parametric radiation generation on polaritons in cubic noncentrosymmetric crystals are studied. The possibility of such generation is theoretically justified. The polariton radiation frequencies are calculated for GaP, ZnSe, ZnTe, and GaAs crystals. The obtained generation frequencies are compared to the experimental results on Raman scattering on polaritons. The block diagram of the terahertz radiation generator operation using a GaP crystal and a pulsed laser with high peak power at low energy of laser pump pulses is presented. The lasing frequency shift is analyzed depending on the scattering geometry. The coefficient of exciting radiation conversion to the terahertz range is determined.     

Asymmetry of the wall shear stress in a stimulated ascendant flow of a liquid with monodisperse bubbles

Results of an experimental investigation of the two-phase wall shear stress averaged over the tube perimeter and the pulsation of wall shear stress in a stimulated ascendant flow with monodisperse bubbles with an average diameter of 1.2 and 2.2 mm are presented. Regimes with various hydrodynamic parameters such as high shear stress on the wall, low and negative wall shear stress, a high level of shear stress pulsation on the wall, and possible decrease in this level of pulsation are found. An increase in the void gas fraction results in a monotonic increase of perturbation of the single-phase flow. The dependences of the ratio of two-phase and single-phase wall shear stresses for two average bubble diameters seem to be qualitatively similar. The analysis of data revealed a complex dependence of the shear stress pulsation on the bubble diameter. The averaged flow characteristics quantitatively change upon the decrease in the bubble diameter. A further decrease in the average bubble diameter at the same void gas fraction will probably increase the heat-and mass-transfer characteristics of the flow. This is an issue for the futures study.     

Mesoscopic superconductors under irradiation: microwave spectroscopy of Andreev states

We show that irradiation of a voltage-biased superconducting quantum point contact at frequencies of the order of the gap energy can remove the suppression of subgap dc transport through Andreev levels. Quantum interference among resonant scattering events involving photon absorption is furthermore shown to make microwave spectroscopy of the Andreev levels feasible. We also discuss how the same interference effect can be applied for detecting weak electromagnetic signals up to the gap frequency, and how it is affected by dephasing and relaxation.     

Nanotubes fabricated from Ni-naphthalocyanine by a template method

Novel naphthalocyanine (Nc) nanotubes with special wall structures were fabricated by a template method using Nc molecules as building blocks. Thermal stabilization of the ordered columnar structures of the tetrakis(tert-butyl)naphthalocyanine (Ni-BNc) molecules, induced from the pi-pi interactions in the nanoscale channels of an alumina template, resulted in Nc nanotubes with walls consisting of well-ordered Nc molecular disks. Further thermal treatment of Ni-BNc at 600 degrees C produced carbonized Nc nanotubes containing ordered columnar, graphitic wall structures with the graphene disks arranged perpendicular to the tube axis. These nanotubes may be useful for extending the application of Nc molecules for nanodevice fabrication.