Floquet–Liouville supermatrix approach. II. Intensity‐dependent generalized nonlinear optical susceptibilities

This is the published version, also available here: http://dx.doi.org/10.1063/1.451981We present a practical n o n p e r t u r b a t i v e method for e x a c t treatment of i n t e n s i t y‐d e p e n d e n t generalized nonlinear optical susceptibilities χ(ω) in intense polychromatic fields, valid for arbitrary laser intensities, detunings, and relaxation. By means of the many‐mode Floquet theory, the time‐dependent Liouville equation can be transformed into an equivalent t i m e‐i n d e p e n d e n t infinite‐dimensional Floquet–Liouville supermatrix (FLSM) eigenvalue problem. It is then shown that the nonlinear optical susceptibilities χ(ω) can be completely determined simply from the supereigenvalues and eigenfunctions of the Floquet–Liouvillian  L̂ F . In addition to this exact FLSM approach, we have also presented higher‐order perturbative results, based on the extension of the Salwen’s nearly degenerate perturbation theory, appropriate for somewhat weaker fields and near‐resonant multiphoton processes, but beyond the conventional perturbative or rotating wave approximation (RWA). In the case of two‐level systems, for example, the implementation of Salwen’s method in the time‐independent L̂ F allows the reduction of the infinite‐dimensional FLSM into a 4×4 dimensional effective Hamiltonian, from which essential a n a l y t i c a l formulas for intensity‐dependent χ(ω) can be obtained. These methods are applied to a detailed study of intensity‐dependent spectralline shapes (such as hole burning and extra resonance peaks at the line center, and the effects of saturation, detuning, and radiative and collisional damping, etc.) and subharmonic structures in nonlinear multiple wave mixings χ[(m+1)ω1−mω2] for two‐level systems in intense linearly polarized bichromatic fields

Zero differential resistance state of two dimensional electron systems in strong magnetic fields

Zero differential resistance state is found in response to direct current applied to 2D electron systems at strong magnetic field and low temperatures. Transition to the state is accompanied by sharp dip of negative differential resistance, which occurs above threshold value $I_{th}$ of the direct current. The state depends significantly on the temperature and is not observable above several Kelvins. Additional analysis shows lack of the linear stability of the 2D electron systems at $I>I_{th}$ and inhomogeneous, non-stationary pattern of the electric current in the zero differential resistance state. We suggest that the dc bias induced redistribution of the 2D electrons in energy space is the dominant mechanism leading to the new electron state.Comment: 5 pages, 3 figure

Light-Induced Atomic Desorption for loading a Sodium Magneto-Optical Trap

We report studies of photon-stimulated desorption (PSD), also known as light-induced atomic desorption(LIAD), of sodium atoms from a vacuum cell glass surface used for loading a magneto-optical trap (MOT). Fluorescence detection was used to record the trapped atom number and the desorption rate. We observed a steep wavelength dependence of the desorption process above 2.6 eV photon energy, a result significant for estimations of sodium vapor density in the lunar atmosphere. Our data fit well to a simple model for the loading of the MOT dependent only on the sodium desorption rate and residual gas density. Up to 3.7x10^7 Na atoms were confined under ultra-high vacuum conditions, creating promising loading conditions for a vapor cell based atomic Bose-Einstein condensate of sodium.Comment: Sodium LIAD loaded MOT, 7 pages, 5 figures. Revised submitted manuscript with minor corrections, new data presented, Fig.5 change

Controlling atomic vapor density in paraffin-coated cells using light-induced atomic desorption

Atomic-vapor density change due to light induced atomic desorption (LIAD) is studied in paraffin-coated rubidium, cesium, sodium and potassium cells. In the present experiment, low-intensity probe light is used to obtain an absorption spectrum and measure the vapor density, while light from an argon-ion laser, array of light emitting diodes, or discharge lamp is used for desorption. Potassium is found to exhibit significantly weaker LIAD from paraffin compared to Rb and Cs, and we were unable to observe LIAD with sodium. A simple LIAD model is applied to describe the observed vapor-density dynamics, and the role of the cell's stem is explored through the use of cells with lockable stems. Stabilization of Cs vapor density above its equilibrium value over 25 minutes is demonstrated. The results of this work could be used to assess the use of LIAD for vapor-density control in magnetometers, clocks, and gyroscopes utilizing coated cells.Comment: 10 pages, 11 figure

Bogolyubov-Hartree-Fock approach to studying the QCD ground state

The quark's behaviour while influenced by a strong stochastic gluon field is analyzed. An approximate procedure for calculating the effective Hamiltonian is developed and the corresponding ground state within the Hartree-Fock-Bogolyubov approach is found. The comparative analysis of various Hamiltonian models is given and transition to the chiral limit in the Keldysh model is discussed in detail.Comment: 18 pages, 4 figures, new version of the manuscrip

Some peculiarities in response on filling up the Fermi sphere by quarks

Considering quarks as the quasi-particles of the model Hamiltonian with four-fermion interaction we study response on the process of filling up the Fermi sphere by quarks.Comment: 11 pages, 5 figures, minor language improvemen

Видный учёный и организатор науки Н. В. Лопатина

The article is written on the jubilee of Natalia Viktorovna Lopatina, Russian scholar, pedagogue, and science leader. Her biography and key activities are reviewed. N. V. Lopatina graduated from Moscow State Institute of Culture (MGIK) in 1992, and since that she has been teaching at the institute; in 1998 she became an associate professor, and later, in 2005, a professor. In 2011, Natalia V. Lopatina was appointed an academic secretary of MGIK Dissertation Board, and since 2020, she has been heading it. Her role in improving the Dissertation Board activities is emphasized. In March 2015, N. V. Lopatina completed her doctoral dissertation in pedagogy. She is the Editor-in-Chief of the professional journal «Culture: Theory and practice»; she also heads the chair of library and information studies (previously, the chair of library studies and bibliology). Today, the chair comprises seven Ph. D. and D. Sc. who are able to solve the most challenging educational, research and intellectual problems. Selected research and academic works by N. V. Lopatina are reviewed in brief.Статья посвящена юбилею Н. В. Лопатиной – российского учёного, педагога, организатора науки. Представлена её биография и основные аспекты деятельности. Завершив обучение в Московском государственном институте культуры в 1992 г., Н. В. Лопатина приступила к преподавательской работе в этом вузе. В 1998 г. Н. В. Лопатина – доцент, а с 2005 г. – профессор МГИКа; в 2011 г. назначена учёным секретарем диссертационного совета при МГИКе, а в 2020 г. возглавила его. Подчёркнута активная деятельность Н. В. Лопатиной по развитию работы диссовета. В марте 2015 г. Н. В. Лопатина успешно защитила диссертацию на соискание учёной степени доктора педагогических наук. Показана её работа в качестве главного редактора профессионального журнала «Культура: теория  и  практика».  Особо  отмечена  деятельность Н. В. Лопатиной на посту заведующей кафедрой библиотековедения и книговедения (впоследствии – кафедры библиотечно-информационных наук). Эта кафедра сейчас способна решать самые сложные научно-творческие и образовательные задачи. Перечислены избранные научно-исследовательские и учебные труды Н. В. Лопатиной, дана их краткая характеристика