Voronezh State University

About: Voronezh State University is a education organization based out in Voronezh, Russia. It is known for research contribution in the topics: Silicon & Boundary value problem. The organization has 5166 authors who have published 6097 publications receiving 31680 citations. The organization is also known as: VSU & Voronezh University.

Optical limiting, nonlinear refraction and nonlinear absorption of the associates of Cd 0.5 Zn 0.5 S quantum dots and dyes.

Abstract: The optical limiting properties of alloyed Cd0.5Zn0.5S quantum dots associated with erythrosine dye are analyzed using 532 nm, 40 ps pulses. We show that joint influence of saturable absorption, reverse saturable absorption and two-photon absorption cause the optical limiting of 532 nm radiation at the pulse energies exceeding 1 mJ. The nonlinear refraction and nonlinear absorption of these quantum dots associated with different organic dyes were studied using 1064 nm and 532 nm radiation. The nonlinear refraction index and nonlinear absorption coefficient of Cd0.5Zn0.5S quantum dots were measured at λ = 1064 nm to be 2 × 10-13 cm2 W-1 and 1.2 × 10-8 cm W-1, while the reverse saturable absorption of Cd0.5Zn0.5S quantum dots and erythrosine at λ = 532 nm was almost two orders larger. The potential applications of these quantum dots for high-order harmonic generation are discussed.

Low- and high-order harmonic generation in the extended plasmas produced by laser ablation of zinc and manganese targets

Abstract: The systematic studies of the harmonic generation of ultrashort laser pulses in the 5-mm-long Zn and Mn plasmas (i.e., application of nanosecond, picosecond, and femtosecond pulses for ablation, comparison of harmonic generation from atomic, ionic, and cluster-contained species of plasma, variation of plasma length, two-color pump of plasmas, etc.) are presented. The conversion efficiency of the 11th–19th harmonics generated in the Zn plasma was ∼5 × 10−5. The role of the ionic resonances of Zn near the 9th and 10th harmonics on the enhancement of harmonics is discussed. The enhancement of harmonics was also analyzed using the two-color pump of extended plasmas, which showed similar intensities of the odd and even harmonics along the whole range of generation. The harmonics up to the 107th order were demonstrated in the case of manganese plasma. The comparison of harmonic generation in the 5-mm-long and commonly used short (≤0.5 mm) plasma plumes showed the advanced properties of extended media.

Lithoheterotrophic growth and electron transfer chain components of the filamentous gliding bacterium Leucothrix mucor DSM 2157 during oxidation of sulfur compounds

Abstract: Evidence is presented that the type strain of filamentous gliding bacterium Leucothrix mucor DSM 2157 is capable of lithoheterotrophic growth. Thiosulfate oxidation was accompanied by accumulation of sulfate and tetrathionate in the growth medium and intracellular accumulation of elemental sulfur, as occurs in filamentous sulfur bacteria of the genus Thiothrix. Thiosulfate oxidation by L. mucor was induced during growth with a limiting concentration of organic substrate (i.e. 50–170 mg l−1 tryptone) and resulted from the induction of dissimilatory enzymes of sulfur metabolism. Metabolically useful energy was derived by both substrate-linked and oxidative phosphorylation from thiosulfate and sulfite oxidation. During sulfite oxidation the electron transfer pathway was shown to begin at the ubiquinone-cytochrome b segment of the electron transport chain. L. mucor limited by organic substrate had lowered levels of membrane bound cytochromes c and respiratory activity but a higher input of a cyanide-insensitive respiratory component than during organic enriched growth. Cytochromes aa3 and d, which had not been shown previously in this bacterium, were detected in the cells under various growth conditions. Cytochrome aa3 is suggested to take part in the electron transfer pathway from thiosulfate to oxygen which was completely inhibited by 100 μM cyanide.

Tunneling Ionization of Atoms with Excitation of the Core

Abstract: A general formula is obtained for the probability of tunneling ionization of an atom accompanied by excitation of the core. This formula is a generalization of the Carlson formula for the probability of a single-photon two-electron transition in atoms. The limiting case of this formula, just as that of the Carlson formula, is the well-known random-perturbations approximation. Numerical results are presented for Zn, Sr, and Cd atoms. For these atoms the contribution of the excited states of singly charged ions to the probability of the formation of doubly charged ions is a nonmonotonic function of the laser radiation intensity. Analysis of the tunneling ionization of molecules shows that with overwhelming probability an ion is formed in the ground vibrational state, while for the standard photoionization the distribution over vibrational states is determined by the Franck-Condon factors.