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.

Potassium spectra in the 700–7000 cm-1 domain: Transitions involving f-, g-, and h-states

Abstract: Context. The infrared (IR) range is becoming increasingly important to astronomical studies of cool or dust-obscured objects, such as dwarfs, disks, or planets, and in the extended atmospheres of evolved stars. A general drawback of the IR spectral region is the much lower number of atomic lines available (relative to the visible and ultraviolet ranges). Aims. We attempt to obtain new laboratory spectra to help us identify spectral lines in the IR. This may result in the discovery of new excited atomic levels that are difficult to compute theoretically with high accuracy, hence can be determined solely from IR lines.Methods. The K vapor was formed through the ablation of the KI (potassium iodide) target by a high-repetition-rate (1.0 kHz) pulsed nanosecond ArF laser (λ = 193 nm, output energy of 15 mJ) in a vacuum (10-2 Torr). The time-resolved emission spectrum of the neutral atomic potassium (K i) was recorded in the 700–7000 cm-1 region using the Fourier transform infrared spectroscopy technique with a resolution of 0.02 cm-1 . The f -values calculated in the quantum-defect theory approximation are presented for the transitions involving the reported K i levels. Results. Precision laboratory measurements are presented for 38 K i lines in the infrared (including 25 lines not measured previously in the laboratory) range using time-resolved Fourier transform infrared spectroscopy. The 6g, 6h, and 7h levels of K i are observed for the first time, in addition to updated energy values of the other 23 K i levels and the f -values for the transitions involving these levels.Conclusions. The recorded wave numbers are in good agreement with the data from the available solar spectrum atlases. Nevertheless, we correct their identification for three lines (1343.699, 1548.559, and 1556.986 cm-1 ).

Nanocrystalline tin dioxide: Basics in relation with gas sensing phenomena. Part I. Physical and chemical properties and sensor signal formation

Abstract: The experimental and theoretical concepts of the physical and chemical properties of tin dioxide which favor its use in semiconductor gas sensors are systematized. The interrelations of the band structure, the nature of intrinsic defects, microstructure parameters, and reactivity of nanocrystalline SnO2 during the detection of gases of different chemical nature are considered. The existing concepts which describe the change in electrical properties and the mechanism of the sensor signal formation are analyzed.

Strong field detachment of a negative ion with non-zero angular momentum: application to F -

Abstract: We apply our recently developed, model-independent quantum approach for intense laser detachment of a weakly bound electron to interpret a recent experiment on above-threshold detachment (ATD) of the F− ion. We find that the measured electron energies correspond to the 'Keldysh part' of the ATD spectrum, just below the onset of our predicted rescattering plateau. Overall, our predicted ATD spectrum (using a scaled peak intensity and focal averaging) is in excellent agreement with the experimental data, except for certain structures observed for electron energies above 12.6 eV that we attribute to known two-electron resonances of F−. A number of analytical approximations to our exact p-state ATD amplitude are obtained, and their accuracy is investigated.

Even harmonic generation in isotropic media of dissociating homonuclear molecules

Abstract: Isotropic gases irradiated by long pulses of intense IR light can generate very high harmonics of the incident field. It is generally accepted that, due to the symmetry of the generating medium, be it an atomic or an isotropic molecular gas, only odd harmonics of the driving field can be produced. Here we show how the interplay of electronic and nuclear dynamics can lead to a marked breakdown of this standard picture: a substantial part of the harmonic spectrum can consist of even rather than odd harmonics. We demonstrate the effect using ab-initio solutions of the time-dependent Schrodinger equation for $H$$_2$$^+$ and its isotopes in full dimensionality. By means of a simple analytical model, we identify its physical origin, which is the appearance of a permanent dipole moment in dissociating homonuclear molecules, caused by light-induced localization of the electric charge during dissociation. The effect arises for sufficiently long laser pulses and the region of the spectrum where even harmonics are produced is controlled by pulse duration. Our results (i) show how the interplay of femtosecond nuclear and attosecond electronic dynamics, which affects the charge flow inside the dissociating molecule, is reflected in the nonlinear response, and (ii) force one to augment standard selection rules found in nonlinear optics textbooks by considering light-induced modifications of the medium during the generation process.