Modifications of high harmonic spectra by ion resonant transitions

High-order harmonic generation is considered in a system consisting of an ion with an internal degree of freedom plus an outer electron. The theoretical treatment is both quantum-mechanical and classical. The emphasis is on the core resonance effects, which can significantly modify the harmonic spectra, with appearance of anomalous peaks. Under some assumptions, the spectral amplitude of the resonant harmonic of the system dipole moment can be obtained by evaluation of such amplitude within a single-electron approximation and multiplication of the result by a correcting factor. The latter depends on the polarizability of the ion and of a free electron at the harmonic frequency. Copyright \ua9 1996 by MAHK Hayka/Interperiodica Publishing

Analysis of Implementation Results of the Distributed Access Control System

This paper attempts to create software and hardware complex that can work autonomously and designed to simplify the organization of scientific conferences. The goal of developing a complex is to give an opportunity to attendees of the conference to register to conference sections using radio frequency identification (RFID) tags and collect statistics of sections attendance in real time. The paper describes the development process of the complex, problems that encounters during the development process and ways to fix it

Development of Low-Budget Spectrum Analyzers for IoT and Sensor Networks

The article describes the development, implementation and research of the work of spectrum analyzers for sensor networks and IoT (2.4 GHz). Comparative analysis of existing available microcontrollers for spectrum analysis, selection of hardware interfaces, ordering of required modules and electrical components have been described in the paper. Several variants of spectrum analyzers were implemented during development

Time-dependent density functional theory: Past, present, and future

Time-dependent density functional theory (TDDFT) is presently enjoying enormous popularity in quantum chemistry, as a useful tool for extracting electronic excited state energies. This article discusses how TDDFT is much broader in scope, and yields predictions for many more properties. We discuss some of the challenges involved in making accurate predictions for these properties.Comment: 12 pages, 4 figure

Multiphoton radiative recombination of electron assisted by laser field

In the presence of an intensive laser field the radiative recombination of the continuum electron into an atomic bound state generally is accompanied by absorption or emission of several laser quanta. The spectrum of emitted photons represents an equidistant pattern with the spacing equal to the laser frequency. The distribution of intensities in this spectrum is studied employing the Keldysh-type approximation, i.e. neglecting interaction of the impact electron with the atomic core in the initial continuum state. Within the adiabatic approximation the scale of emitted photon frequencies is subdivided into classically allowed and classically forbidden domains. The highest intensities correspond to emission frequencies close to the edges of classically allowed domain. The total cross section of electron recombination summed over all emitted photon channels exhibits negligible dependence on the laser field intensity.Comment: 14 pages, 5 figures (Figs.2-5 have "a" and "b" parts), Phys.Rev.A accepted for publication. Fig.2b is presented correctl

Vacancy Defects in Ga2O3: First-Principles Calculations of Electronic Structure

First-principles density functional theory (DFT) is employed to study the electronic structure of oxygen and gallium vacancies in monoclinic bulk β-Ga2 O3 crystals. Hybrid exchange– correlation functional B3LYP within the density functional theory and supercell approach were successfully used to simulate isolated point defects in β-Ga2 O3. Based on the results of our calcu-lations, we predict that an oxygen vacancy in β-Ga2 O3 is a deep donor defect which cannot be an effective source of electrons and, thus, is not responsible for n-type conductivity in β-Ga2 O3. On the other hand, all types of charge states of gallium vacancies are sufficiently deep acceptors with transition levels more than 1.5 eV above the valence band of the crystal. Due to high formation energy of above 10 eV, they cannot be considered as a source of p-type conductivity in β-Ga2 O3. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.Funding: This research was funded by the Science Committee of the Ministry of Education and Science of the Republic of Kazakhstan (Grant No. AP08856540) as well as by the Latvian research council via the Latvian National Research Program under the topic “High-Energy Physics and Accelerator Technologies”, Agreement No: VPP-IZM-CERN-2020/1-0002 for A.I. Popov. In addition, J. Purans is grateful to the ERAF project 1.1.1.1/20/A/057 while A. Platonenko was supported by Latvian Research Council No. LZP-2018/1-0214