[Show abstract][Hide abstract] ABSTRACT: The temporal dynamics of the three dimensional hydrogen atom under the action of an external
electric field is studied by using an analytic model and a numerical simulation. In the stationary case, analytic
expressions for determining the evolution of angular momentum L of the Rydberg electron (RE) are obtained
and significant oscillations of L are noted. Under conditions of the dynamical chaos regime stimulated by a
linearly polarized microwave field, additional specific features of the evolution of L are found with the help
of unification of the equations of motion and numerical calculations. The role of L in the formation of diffu
sion ionization of the RE is revealed.
Optics and Spectroscopy 12/2014; 117(6):861-868. DOI:10.1134/S0030400X14120066 · 0.72 Impact Factor
[Show abstract][Hide abstract] 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 radiation-collisional 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≈10n≈10. 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≈3·104E≈3·104 V/cm for states with n>10n>10. This means that the emission of RA with n≥10n≥10 is effectively blocked for such fields. In the region of lower electric field intensities the double Stark resonance (or Förster 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 Föster 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 long-lived RA states and intensities of corresponding radiative transitions can be associated with the effects of dynamic chaos via collisional ionization. The Föster 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.
Advances in Space Research 10/2014; 54(7):1159–1163. · 1.36 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We investigate theoretically the formation of two-component light with
superluminal group velocity in a medium controlled by four Raman pump fields.
In such an optical scheme only a particular combination of the probe fields is
coupled to the matter and exhibits superluminal propagation, the orthogonal
combination is uncoupled. The individual probe fields do not have a definite
group velocity in the medium. Calculations demonstrate that this superluminal
component experiences an envelope advancement in the medium with respect to the
propagation in vacuum.
Physical Review A 09/2014; 90(3). DOI:10.1103/PhysRevA.90.033827 · 2.81 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A stable symplectic scheme for calculating particle trajectories in time-periodic force fields based on the Floquet technique and split-operator method is described. The dynamics of a three-dimensional hydrogen atom under the action of an external linearly polarized microwave electric field is studied in a numerical experiment. Under conditions of the implemented dynamical chaos, features in the evolution of angular momentum L(t) of a Rydberg electron (RE) that do not meet the assumptions of traditional theoretical approaches for describing light-induced diffusion ionization of the RE are revealed.
Optics and Spectroscopy 07/2014; 117(1):8-17. DOI:10.1134/S0030400X1407008X · 0.72 Impact Factor
[Show abstract][Hide abstract] 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 radiation-collisional 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 long-lived $RA$ 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.
Advances in Space Research 11/2013; 54(7). DOI:10.1016/j.asr.2013.08.028 · 1.36 Impact Factor
[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 Doppler-free arrangement of a collimated supersonic beam of Na2 molecules crossing two counterpropagating laser beams that excite a two-photon transition in a three-level ladder scheme. We propose an analytical two-level 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 density-matrix equations of motion using a split propagation technique and with experimental results.
Physical Review A 07/2012; 86(1). DOI:10.1103/PhysRevA.86.012501 · 2.81 Impact Factor
[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 Doppler-free arrangement of a collimated supersonic beam of Na_2 molecules crossing two counterpropagating laser beams that excite a two-photon transition in a three-level ladder scheme. We propose an analytical two-level 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 density-matrix equations of motion using a split propagation technique and with experimental results.
Physical Review A 07/2012; 86(1):012501. · 2.81 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 magneto-optical trap (MOT). Under ordinary conditions, all spectra exhibit a linewidth of 2-3 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 electric-field 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 02/2012; 114(1):14. DOI:10.1134/S1063776111160102 · 0.88 Impact Factor
[Show abstract][Hide abstract] 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 resonance
Russian Journal of Physical Chemistry B 08/2011; 5(4):537-545. DOI:10.1134/S1990793111040117 · 0.36 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Elementary processes in plasma phenomena traditionally attract physicist's attention. The channel of charged-particle formation in Rydberg atom–atom thermal and sub-thermal collisions (the low temperature plasmas conditions) leads to creation of the molecular ions – associative ionization (AI). atomic ions – Penning-like 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+). Hydrogen-like alkali-metal 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 chemi-ionisation (AI+PI) on Rydberg atom-atom 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 chemi-ionization 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. DOI:10.1088/1742-6596/257/1/012027
[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 gas-dynamic 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 06/2010; 108(6):877-882. DOI:10.1134/S0030400X10060093 · 0.72 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Elementary processes in astrophysical phenomena traditionally attract
researchers attention. At first this can be attributed to a group of
hemi-ionization 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. DOI:10.1016/j.newar.2009.07.003 · 6.43 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 long-range 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 interaction-induced motion of the atoms and the effect of multi-particle systems in this work. We find that the probability for this ionization mechanism can be increased in many-particle 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; DOI:10.1140/epjd/e2009-00119-4 · 1.23 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We have studied ionization of alkali-metal 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 BBR-induced 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 BBR-induced transitions between bound Rydberg states of Li has been found. The calculated ionization rates are compared with our earlier measurements of BBR-induced 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 BBR-induced ionization signal to measurements of collisional ionization rates is demonstrated.
New Journal of Physics 01/2009; 11(1):13052. DOI:10.1088/1367-2630/11/1/013052 · 3.56 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 atom-white 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). DOI:10.1103/PhysRevA.78.053415 · 2.81 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: This paper presents observations and an interpretation of laser-induced excitation and fluorescence in a ladder g-e-f 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 g-e coupling, by cw laser P, is strong. A weak cw laser S couples levels e and f. The basic observations are of level-f fluorescence as a function of the detuning of the S laser from resonance. The signal profile does not appear as the typical Autler-Townes 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 three-level system. We invoke the mechanism of optical pumping and evolution along adiabatic states, together with Landau-Zener 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). DOI:10.1103/PhysRevA.78.053804 · 2.81 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Results of preliminary simulations of Autler-Townes effect in atomic and molecular level systems with hyperfine structure are presented. A system of three states with hyperfine structure in Na and Na 2 coupled in a ladder linkage scheme by a weak probe field and a strong coupling field is studied by solving the density matrix equations of motion. The simulations show that application of a strong coupling field to systems with large hyperfine level splittings leads to a full resolution of M F Zeeman sublevels of the hyperfine levels F. This resolution improves as the coupling field Rabi frequency is increased to values much larger than the hyperfine level separations. In molecules, where hyperfine splittings are very small, the M F Zeeman sublevels can only be resolved at very small coupling field strengths and only if the HF splittings are larger than the natural widths of excited states and the laser linewidths. When the coupling field Rabi frequency exceeds the hyperfine level separations, the M F resolution is completely lost. This effect is interpreted in terms of the formation of dark states when a number of closely lying energy levels are coupled by a strong field to another energy level.
The Fifth International Symposium “Modern Problems of Laser Physics” (MPLP’2008), Novosibirsk; 08/2008
[Show abstract][Hide abstract] 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 quasi-classical formulas for the photoionization cross
sections and for the radial matrix elements of transitions in the discrete spectrum. The effect of the blackbody-radiation-induced
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 high-lying 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):20-27. DOI:10.1134/S1063776108070029 · 0.88 Impact Factor