Publications (70)73.6 Total impact

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ABSTRACT: Radiative and collisional constants of excited atoms contain the matrix elements of the dipole transitions and when they are blocked one can expect occurring a number of interesting phenomena in radiationcollisional kinetics. In recent astrophysical studies of IR emission spectra it was revealed a gap in the radiation emitted by Rydberg atoms ($RA$) with values of the principal quantum number of $n\approx10$. Under the presence of external electric fields a rearrangement of $RA$ emission spectra is possible to associate with manifestations of the Stark effect. The threshold for electric field ionization of $RA$ is $E\approx3\cdot10^{4}$ V/cm for states with $n>10$. This means that the emission of $RA$ with $n\ge10$ is effectively blocked for such fields. In the region of lower electric field intensities the double Stark resonance (or F\"{o}rster resonance) becomes a key player. On this basis it is established the fact that the static magnetic or electric fields may strongly affect the radiative constants of optical transitions in the vicinity of the F\"{o}ster resonance resulting, for instance, in an order of magnitude reduction of the intensity in some lines. Then, it is shown in this work that in the atmospheres of celestial objects lifetimes of comparatively longlived $RA$ states and intensities of corresponding radiative transitions can be associated with the effects of dynamic chaos via collisional ionization. The F\"{o}ster resonance allows us to manipulate the random walk of the Rydberg electron ($RE$) in the manifold of quantum levels and hence change the excitation energies of $RA$, which lead to anomalies in the IR spectra.11/2013;  [Show abstract] [Hide abstract]
ABSTRACT: We revisit transit time broadening for one of the typical experiment designs in molecular spectroscopy, that of a collimated supersonic beam of particles crossing a focused Gaussian laser beam. In particular, we consider a Dopplerfree arrangement of a collimated supersonic beam of Na2 molecules crossing two counterpropagating laser beams that excite a twophoton transition in a threelevel ladder scheme. We propose an analytical twolevel model with a virtual intermediate level to show that the excitation line shape is described by a Voigt profile and provide the validity range of this model with respect to significant experimental parameters. The model also shows that line broadening due to the curvature of laser field wave fronts on the particle beam path is exactly compensated by increased transit time of particles farther away from the beam axis, such that the broadening is determined solely by the size of the laser beam waist. The analytical model is validated by comparing it with numerical simulations of densitymatrix equations of motion using a split propagation technique and with experimental results.Physical Review A 07/2012; 86(1). · 3.04 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: Experiments are carried out on the spectroscopy of the Foerster resonance lines Rb(37P) + Rb(37P) {yields} Rb(37S) + Rb(38S) and microwave transitions nP {yields} n Prime S, n Prime D between Rydberg states of cold rubidium atoms in a magnetooptical trap (MOT). Under ordinary conditions, all spectra exhibit a linewidth of 23 MHz irrespective of the interaction time between atoms or between atoms and microwave radiation, although the limit resonance width should be determined by the inverse interaction time. The analysis of experimental conditions has shown that the main source of line broadening is the inhomogeneous electric field of cold photoions that are generated under the excitation of initial nP Rydberg states by broadband pulsed laser radiation. The application of an additional electricfield pulse that rapidly extracts photoions produced by a laser pulse leads to a considerable narrowing of lines of microwave resonances and the Foerster resonance. Various sources of line broadening in cold Rydberg atoms are analyzed.Journal of Experimental and Theoretical Physics 01/2012; 114:14. · 0.92 Impact Factor 
Article: Specifics of the stochastic ionization of a Rydberg collision complex with Förster resonance
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ABSTRACT: The physics of the formation of dynamic nonlinear resonances in an isolated Rydberg collisional complex is described. The development of the stochastic instability of Rydberg electron trajectories due to charge exchange in the complex is considered. The realization of the resonance in external statistic magnetic and electric fields is predicted to be accompanied by a significant narrowing of areas of stochastic motion with a concurrent decrease in the rates of the ionization of real quasimolecular systems proceeding through the migration over the Rydberg crowding of quantum states. Keywordsdynamic chaos–collisional complex–internal microwave field–stochastic ionization–Förster resonanceRussian Journal of Physical Chemistry B 01/2011; 5(4):537545. · 0.21 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: Elementary processes in plasma phenomena traditionally attract physicist's attention. The channel of chargedparticle formation in Rydberg atom–atom thermal and subthermal collisions (the low temperature plasmas conditions) leads to creation of the molecular ions – associative ionization (AI). atomic ions – Penninglike ionization (PI) and the pair of the negative and positive ions. In our universe the chemical composition of the primordial gas consists mainly of Hydrogen and Helium (H, H−, H+, H2, He,He+). Hydrogenlike alkalimetal Lithium (Li, Li+,Li−) and combinations (HeH+, LiH−, LiH+). There is a wide range of plasma parameters in which the Rydberg atoms of the elements mentioned above make the dominant contribution to ionization and that process may be regarded as a prototype of the elementary process of light excitation energy transformation into electric one. The latest stochastic version of chemiionisation (AI+PI) on Rydberg atomatom collisions extends the treatment of the "dipole resonant" model by taking into account redistribution of population over a range of Rydberg states prior to ionization. This redistribution is modelled as diffusion within the frame of stochastic dynamic of the Rydberg electron in the Rydberg energy spectrum. This may lead to anomalies of Rydberg atom spectra. Another result obtained in recent time is understanding that experimental results on chemiionization relate to the group of mixed Rydberg atom closed to the primary selected one. The Rydberg atoms ionisation theory today makes a valuable contribution in the deterministic and stochastic approaches correlation in atomic physic.Journal of Physics Conference Series 12/2010; 257(1):012027.  [Show abstract] [Hide abstract]
ABSTRACT: The formation of the Doppler contour P D(?) of absorption lines upon the excitation of particles in the volume of a gasdynamic beam by light propagating in a direction orthogonal (reduced) to the beam axis is analyzed. Integral representations of P D(?) are obtained for arbitrary relations between the nozzle outlet diameter D and the collimating aperture diameter B in the excitation region are obtained. An optimal configuration at which the reduced Doppler contour is the narrowest at a high density of beam particles is revealed to be B/D = 2.Optics and Spectroscopy 01/2010; 108(6):877882. · 0.56 Impact Factor 
Article: Rydberg atoms in astrophysics
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ABSTRACT: Elementary processes in astrophysical phenomena traditionally attract researchers attention. At first this can be attributed to a group of hemiionization processes in Rydberg atom collisions with ground state parent atoms. This processes might be studied as a prototype of the elementary process of the radiation energy transformation into electrical one. The studies of nonlinear mechanics have shown that so called regime of dynamic chaos should be considered as typical, rather than exceptional situation in Rydberg atoms collision. From comparison of theory with experimental results it follows that a such kind of stochastic dynamic processes, occurred during the single collision, may be observed.New Astronomy Reviews 08/2009; 53:259–265. · 1.82 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We investigate a possible mechanism for the autoionization of ultracold Rydberg gases, based on the resonant coupling of Rydberg pair states to the ionization continuum. Unlike an atomic collision where the wave functions begin to overlap, the mechanism considered here involves only the longrange dipole interaction and is in principle possible in a static system. It is related to the process of intermolecular Coulombic decay (ICD). In addition, we include the interactioninduced motion of the atoms and the effect of multiparticle systems in this work. We find that the probability for this ionization mechanism can be increased in manyparticle systems featuring attractive or repulsive van der Waals interactions. However, the rates for ionization through resonant dipole coupling are very low. It is thus unlikely that this process contributes to the autoionization of Rydberg gases in the form presented here, but it may still act as a trigger for secondary ionization processes. As our picture involves only binary interactions, it remains to be investigated if collective effects of an ensemble of atoms can significantly influence the ionization probability. Nevertheless our calculations may serve as a starting point for the investigation of more complex systems, such as the coupling of many pair states proposed in [Tanner et al., PRL 100, 043002 (2008)].The European Physical Journal D 04/2009; · 1.51 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We have studied ionization of alkalimetal Rydberg atoms by blackbody radiation (BBR). The results of theoretical calculations of ionization rates of Li, Na, K, Rb and Cs Rydberg atoms are presented. The calculations have been performed for nS, nP and nD states for principal quantum numbers n = 8–65 at ambient temperatures of 77, 300 and 600 K. The calculations take into account the contributions of BBRinduced redistribution of population between Rydberg states prior to photoionization and field ionization by extraction electric field pulses. The obtained results show that these phenomena affect both the magnitude of the measured ionization rates and their n dependence. A Cooper minimum for BBRinduced transitions between bound Rydberg states of Li has been found. The calculated ionization rates are compared with our earlier measurements of BBRinduced ionization rates of Na nS and nD Rydberg states with n = 8–20 at 300 K. Good agreement for all states except nS with n >15 is observed. Useful analytical formulae for quick estimates of BBR ionization rates of Rydberg atoms are presented. Application of BBRinduced ionization signal to measurements of collisional ionization rates is demonstrated.New Journal of Physics 01/2009; 11:13052. · 4.06 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: The formation of dark states under an interaction of degenerate atomic states with incoherent broadband radiation (white light) is discussed. A simple coupling scheme in a three level Λ system, which allows both qualitative and quantitative analysis, is discussed. We found a stationary solution of the optical Bloch equations in a broad excitation line approximation that describes the dynamics of the atomwhite light interaction and demonstrated its identity to a conventional dark state created with coherent laser fields. We than examine the efficiency of the population transfer induced by broadband radiation in a model Λ system and revealed that high efficiency (attaining 100%) of stimulated Raman adiabatic passagelike processes can be achieved with certain temporal control of light polarization. The corresponding criterion of adiabaticity was formulated and justified by means of numerical simulations.Physical Review A 11/2008; 78(5). · 3.04 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: This paper presents observations and an interpretation of laserinduced excitation and fluorescence in a ladder gef of three molecular levels [X 1Σg+(v″=0,J″=7), A 1Σu+(v′=10,J′=8), and 5 1Σg+(v=10,J=9), respectively] observed in a supersonic molecular beam of Na2. The ge coupling, by cw laser P, is strong. A weak cw laser S couples levels e and f. The basic observations are of levelf fluorescence as a function of the detuning of the S laser from resonance. The signal profile does not appear as the typical AutlerTownes doublet, but as a spectral structure, whose position, width, and shape depend upon several laser parameters. We interpret these results using a simple model of three nondegenerate quantum states coherently excited while undergoing population loss to states outside the threelevel system. We invoke the mechanism of optical pumping and evolution along adiabatic states, together with LandauZener transition probabilities. We also present results from numerical studies, which include all quantum states, all radiative couplings, coherent and incoherent, as well as convolutions with the relevant distribution functions (velocities and Zeeman sublevels). Although no adjustable parameters are involved, excellent agreement with the experiment is found. Since successive avoided crossings of adiabatic eigenvalues occur, interference effects may be relevant. Such effects are not expected to be visible in the present experiment, for reasons that are discussed. However, we discuss conditions which would allow resolving the interference structure experimentally. We also suggest possible interesting applications of the interference to rapidly switch off Rydberg state population or to control its spatial distribution.Physical Review A 11/2008; 78(5). · 3.04 Impact Factor 
Article: Ionization of nS , nP , and nD lithium, potassium, and cesium Rydberg atoms by blackbody radiation
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ABSTRACT: The results of theoretical calculations of the blackbody ionization rates of lithium, potassium, and cesium atoms residing in Rydberg states are presented. The calculations are performed for nS, nP, and nD states in a wide range of principal quantum numbers, n = 8−65, for blackbody radiation temperatures T = 77, 300, and 600 K. The calculations are performed using the known quasiclassical formulas for the photoionization cross sections and for the radial matrix elements of transitions in the discrete spectrum. The effect of the blackbodyradiationinduced population redistribution between Rydberg states on the blackbody ionization rates measured under laboratory conditions is quantitatively analyzed. Simple analytical formulas that approximate the numerical results and that can be used to estimate the blackbody ionization rates of Rydberg atoms are presented. For the S series of lithium, the rate of population of highlying Rydberg levels by blackbody radiation is found to anomalously behave as a function of n. This anomaly is similar to the occurrence of the Cooper minimum in the discrete spectrum.Journal of Experimental and Theoretical Physics 06/2008; 107(1):2027. · 0.92 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We analyze nonlinear radiation imprisonment (RI) effects in an optically thick vapor in different temperature regimes. An analytical approach is proposed to treat nonlinear decay problems. Special attention is paid to vapor samples having curvilinear geometries (cylinder, sphere) and being excited by a strong laser pulse. We derive a number of new formulas for different radiative trapping factors as functions of opacity and propose a general approach for RI evaluation allowing us to deal with samples both at room and low, or very low, temperatures, such as those customarily achieved in magnetooptical trap (MOT) experiments. As a result, we predict a “subnatural” decay of radiation escaping from cold vapors, which can be envisioned as the basis for a sensitive and reliable MOT diagnostic tool.Physical Review A 06/2008; 77(6). · 3.04 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: Detailed analysis of spectral line broadening and variations in relative intensities of hyperfine spectral components due to optical pumping is presented. Hyperfine levels of sodium 3p 1/2 and 3p 3/2 levels are selectively excited in a supersonic beam at various laser intensities under the conditions when optical pumping time is shorter than transit time of atoms through the laser beam. The excitation spectra exhibit significant line broadening at laser intensities well below the saturation intensity, and redistribution of intensities of hyperfine spectral components is observed, which in some cases is contradicting with intuitive expectations. Theoretical analysis of the dynamics of optical pumping shows that spectral line broadening sensitively depends on the branching coefficient of the laserdriven transition. Analytical expressions for branching ratio dependent critical Rabi frequency and critical laser intensity are derived, which give the threshold for onset of noticeable line broadening by optical pumping. The critical laser intensity has its smallest value for transitions with branching coefficient equal to 0.5, and it can be much smaller than the saturation intensity. Transitions with larger and smaller branching coefficients are relatively less affected. The theoretical excitation spectra were calculated numerically by solving density matrix equations of motion using the split propagation technique, and they wellreproduce the observed effects of line broadening and peak intensity variations. The calculations also show that presence of dark i.e., not laser coupled Zeeman sublevels in the lower state results in effective branching coefficients which vary with laser intensity and differ from those implied by the sum rules, and this can lead to peculiar changes in peak ratios of hyperfine components of the spectra.Physical Review A 01/2008; 77:042511. · 3.04 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: The empirical regularities in the variation of the radiative lifetimes τk of excited states of atoms are reviewed. A quasiclassical theory of radiation damping processes is constructed. The formalism of quantization of the natural width Ak = τk−1 of the excited states of atoms and ions is presented. The question of how to describe the serial dependences for a perturbed series is investigated. It is demonstrated that the radiation emission of atomic systems is sharply reduced when the classical factors in the radiative processes are suppressed. Schemes are proposed for extrapolating lifetimes from the lower terms of a series to the upper Rydberg states, right up to the continuum. Recommended values of τk for group I, II, and VIII atoms are given in a form that is convenient for inclusion in a computerized data base.Soviet Physics Uspekhi 10/2007; 34(1):1. 
Conference Paper: Ionization of Rb and Na Rydberg atoms by blackbody radiation
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ABSTRACT: This work presents the results of the numerical calculations of (blackbody radiation) BBRinduced photoionization rates of Rb and Na Rydberg nS, nP and nD atoms with n = 865 at the ambient temperatures of 77, 300 and 600 K.Lasers and ElectroOptics, 2007 and the International Quantum Electronics Conference. CLEOEIQEC 2007. European Conference on; 07/2007  [Show abstract] [Hide abstract]
ABSTRACT: The chemiionization processes in thermal and subthermal collisions of excited alkali atoms with atoms in ground and excited states were considered, with a particular accent to the applications for geocosmical plasma research. An improved version of semiclassical method for the rate coefficients calculation is presented. The method is applied to the cases of excited alkali atoms with the principal quantum numbers 5 ⩽ n ⩽ 25. The results of calculation of the considered chemiionization processes rate coefficients are compared to the existing experimental data. Their good agreement recommends to use the rate coefficients obtained for analysis of geocosmical plasma processes.New Astronomy Reviews. 04/2007;  [Show abstract] [Hide abstract]
ABSTRACT: Results of theoretical calculations of ionization rates of Rb and Na Rydberg atoms by blackbody radiation BBR are presented. Calculations have been performed for nS, nP, and nD states of Na and Rb, which are commonly used in a variety of experiments, at principal quantum numbers n =8–65 and at three ambient temperatures of 77, 300, and 600 K. A peculiarity of our calculations is that we take into account the contributions of BBRinduced redistribution of population between Rydberg states prior to photoionization and field ionization by extraction electric field pulses. The obtained results show that these phenomena affect both the magnitude of measured ionization rates and shapes of their dependences on n. The calculated ionization rates are compared with the results of our earlier measurements of BBRinduced ionization rates of Na nS and nD Rydberg states with n =8–20 at 300 K. A good agreement for all states except nS with n 15 is observed. We also present the useful analytical formulas for the quick estimation of BBR ionization rates of Rydberg atoms.Physical Review A 03/2007; · 3.04 Impact Factor
Publication Stats
220  Citations  
73.60  Total Impact Points  
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Institutions

2013

University of Latvia
Rija, Rīga, Latvia


1995–2012

Saint Petersburg State University
 • Faculty of Physics
 • Institute of Radiophysics
SanktPeterburg, St.Petersburg, Russia


2005

Technische Universität Kaiserslautern
 Fachbereich für Physik
Kaiserslautern, RhinelandPalatinate, Germany


1998

Leningrad State University
SanktPeterburg, St.Petersburg, Russia


1985

University of Zagreb
Zagrabia, Grad Zagreb, Croatia
