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.

Estimation of the number of orthogonal signals with unknown parameters

Abstract: Algorithms for estimation of the number of signals with unknown amplitudes and several non-energy parameters are synthesized on the basis of the modified maximum likelihood method. Asymptotic values of the probabilities of the error in estimation of the signal number are determined. The effect of a reduced volume of the a priori domain of possible values and the dimensionality of the vector of unknown non-energy parameters on the quality of operation of the algorithms for estimation of the number of signals is investigated.

Spectral characteristics of CdS quantum dots and their associates with dye molecules dispersed in gelatin

Abstract: A sol–gel method for the production of open quantum dots of CdS measuring 2-5 nm and their associates with dye molecules [methylene blue and the pyridinium salt of 3,3′-di(γ-sulfopropyl)-9-ethyl-4,5,4′,5′-dibenzothiacarbocyaninebetaine] dispersed in gelatin is described. Their spectral characteristics are analyzed. Evidence is obtained for the formation of hybrid associates of CdS quantum dots with monomers of the first and J-aggregates of the second dye.

Nonlinear single and double ionization of molecules by strong laser pulses

Abstract: We present a theoretical treatment for the single and double ionization of molecules in strong laser pulses, including the effect of electron correlations. Applied to a model N2 molecule, our simulations show that double ionization occurs via a direct two-electron mechanism at moderate laser intensities , while a step-by-step sequential ionization process dominates at higher intensity . At intermediate intensity, these two mechanisms have a comparable contribution to the total double-ionization yield. This phenomenon is directly reflected in the spatial distributions of N2+ and N22+ in the focal volume of the laser pulse. In addition we show that at high intensity the singly and doubly charged molecular ions are created in well separated regions of space.

On domains of {\cal P}{\cal T} symmetric operators related to −y''(x) + (− 1)nx2ny(x)

Abstract: In recent years a generalization of Hermiticity has been investigated using a complex deformation H = p2 + x2(ix) of the harmonic oscillator Hamiltonian, where is a real parameter. These complex Hamiltonians, possessing symmetry (the product of parity and time reversal), can have a real spectrum. We will consider the most simple case: even. In this paper we describe all self-adjoint (Hermitian) and at the same time symmetric operators associated with H = p2 + x2(ix). Surprisingly, it turns out that there is a large class of self-adjoint operators associated with H = p2 + x2(ix) which are not symmetric.

Low- and high-order nonlinear optical properties of Ag2S quantum dot thin films

Abstract: Abstract Thin films containing small-sized quantum dots (QDs) and nanoparticles have shown strong optical nonlinearities caused by the confinement effect. Here, we report the study of third-order optical nonlinearities of silver sulfide (Ag2S) QD thin films using 800 and 400 nm, 30 fs pulses. The absorption spectrometry and transmission electron microscopy are used to characterize the synthesized 80 and 500 nm Ag2S QD films. The giant enhancement of nonlinearities is observed up to three to six orders of magnitude larger compared to those for the bulk and liquid Ag2S samples. We also demonstrate the efficient high-order harmonic generation in the plasmas produced during ablation of the Ag2S QD thin films. The analysis of the dynamics of the QD-containing plasma spreading allowed optimization of the delay between the heating and the driving pulses for an enhancement of harmonics conversion efficiency.