Multiwavelength Q-switched CO2 laser with continuous discharge

A low-pressure (20 mbar) CO₂ laser allows to extract pulses at several selected wavelengths simultaneously from the same active medium. We demonstrated this, using an industrial laser modified by a Q-switch and a resonator with two branches. In one branch the wavelengths are spatially separated, whereas in the other they oscillate in one common transverse mode. We designed a multi-wavelength resonator which requires a single additional reflector compared to usual laser cavities. It provided tunable oscillation at six wavelength simultaneously.     

Origin of incommensurate spin modulation in La<Subscript>2−<Emphasis Type="Italic">x</Emphasis></Subscript>Sr<Subscript>x</Subscript>CuO<Subscript>4</Subscript>

A model for explaining incommensurate spin modulation observed in La_2?xSr_xCuO₄ is proposed without assuming stripe formation. In this model, all features of the observed spin textures in the entire doping range are associated only with the geometrical relations for the square lattice and with the competition between various forms of ordering of Sr ions.     

Mechanism of carrier generation and the origin of the pseudogap and 60 K phases in YBCO

The mechanism of hole carrier generation is considered in the framework of a model assuming the formation of negative U centers (NUCs) in HTSC materials under doping. The calculated dependences of carrier concentration on the doping level and temperature are in quantitative agreement with experiment. An explanation is proposed for the pseudogap and 60 K phases in YBa₂Cu₃O_6+δ. It is assumed that a pseudogap is of superconducting origin and arises at temperature T* > T_c∞ > T_c in small nonpercolating clusters as a result of strong fluctuations in the occupancy of NUCs (T_c∞ and T_c are the superconducting transition temperatures of an infinitely large and finite NUC clusters, respectively). The T*(δ) and T_c(δ) dependences calculated for YBa₂Cu₃O_6+δ correlate with experimental dependences. In accordance with the model, the region between T*(δ) and T_c(δ) is the range of fluctuations in which finite nonpercolation clusters fluctuate between the superconducting and normal states due to NUC occupancy fluctuations.     

Peculiarities of discontinuous sequential micro-oxidation of coke on zeolite catalysts

Along with oxidation of hydrogen-containing coke structures, we have observed oxidation of compact accumulations of hydrogen-free coke and as a result we can quantitatively differentiate between outer-surface and intraporous burned coke, and the intraporous coke in turn can be quantitatively distributed over the different elements of the zeolite structures. Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 45, No. 3, pp. 185–189, May–June, 2009.     

Incorporation of hafnium (IV) into KTP framework from phosphate‐fluoride fluxes

Solid solutions KTi_1‐XHf_XOPO₄ (х = 0.008 – 0.107) possessing the KTiOPO₄ structure, have been synthesized in molten system K₂O‐P₂O₅‐TiO₂‐HfF₄. The crystal growth experiment of Hf‐doped KTP crystal has been reported. The X‐ray powder diffraction data and chemical analysis are also presented. It has been shown that KTiOPO₄ crystal structure slightly changes when Hf incorporates into the framework. Transmission/absorption spectra of KTi_0.974Hf_0.026OPO₄ crystals have been recorded. The incorporation of Hf ions shifts the optical absorption edge in the UV‐visible spectrum towards the long‐wavelength region with absorption near 387 nm.     

Macroscopic enrichment of12C by a high-power mechanically Q-switched CO2 laser

The isotope-selective multiphoton dissociation of CHClF₂ in a multipass refocusing Herriott cell was used to enrich more than 4 moles of chlorodifluoromethane to 99.99% of¹²C isotopic purity. It is the largest isotope quantity ever separated by a laser process. A cw excited mechanically Q-switched CO₂ laser, which delivers 16 mJ pulses at 5 kHz was used. The enrichment controlled by a mass-spectrometer and guided by a PC was run with a rate of 25 g¹²C per 24 h.     

New Method for Preparing Tetraphenylbismuth Arenesulfonate

Russian Journal of General Chemistry -     

Adduct of Triphenylphosphine Oxide and Sulfuric Acid: Synthesis and Structure

Adduct of triphenylphosphine oxide and sulfuric acid was synthesized by reacting arenesulfonic acids with triphenylphosphine oxide (1 : 2) in the presence of the moisture of air. According to the X-ray diffraction data, the phosphorous atom has a distorted tetrahedral coordination. The sulfuric acid molecule is disordered over two sites and is linked with two triphenylphosphine oxide molecules through hydrogen bonds.