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

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

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

Experiment for Testing Special Relativity Theory

An experiment aimed at testing special relativity via a comparison of the velocity of a non matter particle (annihilation photon) with the velocity of the matter particle (Compton electron) produced by the second annihilation photon from the decay Na-22(beta^+)Ne-22 is proposed.Comment: 7 pages, 1 figure, Report on the Conference of Nuclear Physics Division of Russian Academy of Science "Physics of Fundamental Interactions", ITEP, Moscow, November 26-30, 200

Loading a vapor cell magneto-optic trap using light-induced atom desorption

Low intensity white light was used to increase the loading rate of $^{87}$Rb atoms into a vapor cell magneto-optic trap by inducing non-thermal desorption of Rb atoms from the stainless steel walls of the vapor cell. An increased Rb partial pressure reached a new equilibrium value in less than 10 seconds after switching on the broadband light source. After the source was turned off, the partial pressure returned to its previous value in $1/e$ times as short as 10 seconds.Comment: 7 pages, 6 figure

Spectral functions of the spinless Holstein model

An analytical approach to the one-dimensional spinless Holstein model is proposed, which is valid at finite charge-carrier concentrations. Spectral functions of charge carriers are computed on the basis of self-energy calculations. A generalization of the Lang-Firsov canonical transformation method is shown to provide an interpolation scheme between the extreme weak- and strong-coupling cases. The transformation depends on a variationally determined parameterthat characterizes the charge distribution across the polaron volume. The relation between the spectral functions of polarons and electrons, the latter corresponding to the photoemission spectrum, is derived. Particular attention is paid to the distinction between the coherent and incoherent parts of the spectra, and their evolution as a function of band filling and model parameters. Results are discussed and compared with recent numerical calculations for the many-polaron problem.Comment: 20 pages, 15 figures, final versio

Universality of the Gunn effect: self-sustained oscillations mediated by solitary waves

The Gunn effect consists of time-periodic oscillations of the current flowing through an external purely resistive circuit mediated by solitary wave dynamics of the electric field on an attached appropriate semiconductor. By means of a new asymptotic analysis, it is argued that Gunn-like behavior occurs in specific classes of model equations. As an illustration, an example related to the constrained Cahn-Allen equation is analyzed.Comment: 4 pages,3 Post-Script figure

Nonequilibrium phenomena in high Landau levels

Developments in the physics of 2D electron systems during the last decade have revealed a new class of nonequilibrium phenomena in the presence of a moderately strong magnetic field. The hallmark of these phenomena is magnetoresistance oscillations generated by the external forces that drive the electron system out of equilibrium. The rich set of dramatic phenomena of this kind, discovered in high mobility semiconductor nanostructures, includes, in particular, microwave radiation-induced resistance oscillations and zero-resistance states, as well as Hall field-induced resistance oscillations and associated zero-differential resistance states. We review the experimental manifestations of these phenomena and the unified theoretical framework for describing them in terms of a quantum kinetic equation. The survey contains also a thorough discussion of the magnetotransport properties of 2D electrons in the linear response regime, as well as an outlook on future directions, including related nonequilibrium phenomena in other 2D electron systems.Comment: 60 pages, 41 figure

Spectrometric method to detect exoplanets as another test to verify the invariance of the velocity of light

Hypothetical influences of variability of light velocity due to the parameters of the source of radiation, for the results of spectral measurements of stars to search for exoplanets are considered. Accounting accelerations of stars relative to the barycenter of the star - a planet (the planets) was carried out. The dependence of the velocity of light from the barycentric radial velocity and barycentric radial acceleration component of the star should lead to a substantial increase (up to degree of magnitude) semi-major axes of orbits detected candidate to extrasolar planets. Consequently, the correct comparison of the results of spectral method with results of other well-known modern methods of detecting extrasolar planets can regard the results obtained in this paper as a reliable test for testing the invariance of the velocity of light.Comment: 11 pages, 5 figure