Novel nonperipheral octa-3-hydroxypropylthio substituted metallo-phthalocyanines: synthesis,characterization, and investigation of their electrochemical,photochemical and computational properties

The current study describes the synthesis, electrochemical, computational, and photochemical properties of octa (3-hydroxypropylthio) substituted cobalt (II) ( 4 ), copper (II) ( 5 ), nickel (II) ( 6 ) and zinc(II) ( 7 ) phthalocyanine derivatives. These novel compounds were characterized by elemental analysis,¹H,¹³C NMR, FT-IR, UV-Vis, and MS. The redox behaviors of these metallo-phthalocyanines were investigated by the cyclic voltammetric method. The optimized molecular structure and gauge-including atomic orbital (GIAO)¹H and¹³C NMR chemical shift values of these phthalocyanines in the ground state had been calculated by using B3LYP/6–31G(d,p) basis set. The outcomes of the optimized molecular structure were given and compared with the experimental NMR values. The photochemical properties including photodegradation and singlet oxygen generation of zinc(II) phthalocyanine were studied in DMSO solution for the determination of its photosensitizer behaviors.     

Sensitivity of integrated optical sensors based on a prism coupler

Errors of registration of complex mode propagation constant increments for the sensors with a film waveguiding structure deposited on the base of the prism coupler are investigated. Possibilities for minimization of mean square errors of the registration by choosing parameters of the waveguiding structure and the exciting light beam are determined. As an example, the optimized sensor of ammonia concentration in air is analysed.     

On the methodology of Mössbauer spectroscopy with67Zn

Conclusions The piezoceramic vibrators have the advantages of simplicity and stability of operation over those with quartz plates. However, the former show mechanical hysteresis causing distortions of the motion. This effect can be reduced by an appropriate choice of the ceramic cylinder, but it is not completely avoidable. That is why these distortions should be taken into account or quartz vibrators should be used in precision measurements. The displacement piezoceramic sensor described here gives new methodological opportunities in assembling and preliminary testing of the vibrators to find the optimum of construction and operating conditions as well as for continuous motion control during spectrum accumulation and eventual corrections of the motion distortions.     

Mixing of XeCl laser and mode-Locked Nd:YAG laser radiation in KDP crystal

This paper reports the first direct application of an excimer laser in phase matched mixing experiments. The sum and difference frequency of the radiation of a XeCl excimer laser and a mode-locked Nd:YAG laser were generated in KDP crystals. The energy of the obtained single subnanosecond pulses at 239 nm and 434 nm were almost 50% and 25%, respectively of the excimer laser energy taking part in the nonlinear interaction.     

Self-action of light beams in nonlinear media: soliton solutions

The behaviour of light beams in nonlinear media (self-focussing of optical beams as well as self-modulation and transmission of optical pulses) is considered in the case when the nonlinear polarization contains susceptibilities of third- and fifth-order. The soliton solutions are obtained for the nonlinear equations deduced.     

Optical nonlinearity of azodye-doped polymer waveguides

Results of investigations of the optical and photochromic properties of waveguides prepared by chemical diffusion of the azodyes methyl red and Sudan G into polycarbonate are reported. High optical nonlinearity of the layers is observed under conditions of self-action of λ=633 nm laser radiation, and the mechanism of this effect is established. Zh. Tekh. Fiz. 68, 124–126 (February 1998)     

Study of magnetoresistance and conductance of bicrystal grain boundary in La0.67Ba0.33MnO3 thin film

La_0.67Ba_0.33MnO₃ (LBMO) thin film is deposited on a 36.7°C SrTiO₃ bicrystal substrate using laser ablation technique. A microbridge is created across bicrystal grain boundary and its characteristics are compared with a microbridge on the LBMO film having no grain boundary. Presence of grain boundary exhibits substantial magnetoresistance ratio (MRR) in the low field and low temperature region. Bicrystal grain boundary contribution in MRR disappears at temperature T>175 K. At low temperature, I-V characteristic of the microbridge across bicrystal grain boundary is nonlinear. Analysis of temperature dependence of dynamic conductance-voltage characteristics of the bicrystal grain boundary indicates that at low temperatures (T<175 K) carrier transport across the grain boundary in LBMO film is dominated by inelastic tunneling via pairs of manganese atoms and tunneling through disordered oxides. At higher temperatures (T>175 K), magnetic scattering process is dominating. Decrease of bicrystal grain boundary contribution in magnetoresistance with the increase in temperature is due to enhanced spin-flip scattering process.     

Study of the peak effect phenomenon in single crystals of 2H-NbSe2

The weakly pinned single crystals of the hexagonal 2H-NbSe₂ compound have emerged as prototypes for determining and characterizing the phase boundaries of the possible order-disorder transformations in the vortex matter. We present here a status report based on the ac and dc magnetization measurements of the peak effect phenomenon in three crystals of 2H-NbSe₂, in which the critical current densities vary over two orders of magnitude. We sketch the generic vortex phase diagram of a weakly pinned superconductor, which also utilizes theoretical proposals. We also establish the connection between the metastability effects and pinning.