Three-body recombination of atomic ions with slow electrons

Using the time-dependent wave-packets method, we have quantum mechanically investigated the three-body recombination process for electron energies varying from 10 to 0.01 eV. The classical "bottleneck" prediction on the probable population was confirmed by our S-wave quantum calculations for electron kinetic energies (K(E)) as low as 0.1 eV. But for K(E)<0.1 eV, the quantum three-body recombination tends to populate lower n levels than the classical theory predicted. We also find that, in the same n level, the recombination tends to populate higher angular-momentum states with K(E) decreasing. These results may shed light on the intrinsic dynamics of both ultracold plasmas and frozen Rydberg gases.     

Three-body recombination of ions with electrons in cooler-storage rings

Three-body recombination (TBR) of bare ions with free electrons of anisotropic velocity distribution is discussed in the context of recombination experiments in cooler-storage rings. The recombination rates are derived from the electron impact ionization rates using the modified Saha equation. Analytical expressions for the TBR rates and new scaling rules with main quantum number n, atomic number Z, and both transverse and longitudinal electron temperatures are derived for the low n-states regime probed in experiments in cooler-storage rings. In this context, the discrepancies found between measured rates and predictions for radiative recombination for the e + Ne¹⁰⁺ system [Gao et al., Phys. Rev. Lett. 75 (1995) 4381] are discussed. Present results show that TBR rates for the flattened electron beam velocity distribution cannot account for the recombination enhancement observed at very low relative energies. This revised version was published online in August 2006 with corrections to the Cover Date.     

Statistical dynamics of direct three-body recombination of heavy ions in the presence of argon and xenon atoms

Recombination of singly charged heavy Cs⁺ and Br^– ions with stabilization with neutral Ar or Xe atoms was studied by the classic trajectory method in the range of ion collision energy and third body energy from 1 to 10 eV. The elementary reaction of recombination was studied on the potential energy surface (PES), which quantitatively reproduces the experimental results of collision-induced dissociation of CsBr molecules (the reverse of recombination). An analysis of the statistically reliable number of trajectories revealed a complex multifactor dynamics of recombination, which involves various mechanisms whose realization depends both on the mass and energy ratio of colliding particles and on the PES structure and spatial configurations of collision determined by impact parameters, orientation angles, etc. The molecules that formed as a result of recombination have nonequilibrium vibrational energy distributions and rotational energy distributions comparable to equilibrium.     

Three-body collisions between laser-excited Na and K atoms in the presence of buffer gas

Summary Energy pooling in alkali vapour mixtures has been previously investigated by us in an amalgam of sodium and potassium. In this paper we describe the peculiar features appearing when some buffer gas is introduced in the cell. We demonstrate that the buffer gas enhances the energy transfer between Na(3P) and K(4S), which is detected through the effects induced on the highly excited states populated by the Na(3P)/Na(3P) and K(4P)/K(4P) collisions.

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Riassunto Abbiamo in precedenza studiato il processo di collisione di energy pooling in una miscela di sodio e potassio. In questo lavoro si analizzano i particolari effetti indotti dalla presenza di alcuni Torr di gas tampone introdotti nella cella. Viene dimostrato che il gas tampone favorisce il processo di trasferimento di energia fra Na(3P) e K(4S), che viene rivelato attraverso gli effetti indotti sugli stati altamente eccitati popolati dalle collisioni Na(3P)/Na(3P) e K(4P)/K(4P).

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Резюме Ранее авторы в амальгаме натрия и калия исследовали распределение энергии в смесях щелочных паров. В этой статье мы описываем особенности, возникающие при введении буферного газа в ячейку. Мы поквзываем, что буферный газ усиливает обмен энергией между Na(3P) и K(4S), который детектируется через эффекты, связанные с высоко возбужденными состояниями, заселенными при Na(3P)/Na(3P) и K(4P)/K(4P) соударенияш.

     

Resonances at collisions of slow electrons with cadmium atoms and ions

Using the crossed-beam method and a hypocycloidal electron spectrometer, the energy dependence of the ionization cross section for the cadmium atom has been studied in the near-threshold region and the elastic scattering of slow electrons at an angle close to 180° by Cd⁺ ions was studied for the first time. Within the region under study (0–7 eV above the first atomic ionization potential), a resonance structure determined by the contribution of atomic autoionization states is revealed in both the ionization curve and differential cross section of elastic scattering. The structure in the measured curves has been analyzed with the use of data on the ejected-electron spectra obtained under the excitation of autoionization states of Cd atoms, as well as the data on the optical excitation functions for the atomic spectral lines at λ=430.7 nm (5¹ P ₁-8¹ S ₀), 515.5 nm (5¹ P ₁-7¹ S ₀), 298.0 nm (5³ P ₂-6³ D _j ), and 361.0 nm (5³ P ₂-5³ D _j ).     

The temperature distributions of the electrons,atoms and ions in aerodynamic radiative transfer

The time-dependent individual specie equations specifying conservation of mass, energy and linear momentum for electrons, atoms and ions are solved, together with the transfer equation for continuum radiation, for several specific situations. We assume the temperature of the atoms and ions to be equal, but different to the electron temperature. An ionising disturbance is propagated through a physically idealistic radiating medium and it is shown that the time-development of the differences in temperature distributions are such as to sufficiently affect the absorption and emission properties of the gas, and thus, the emergent flux intensities.     

Three-particle recombination of non-hydrogen-like ions in the presence of plasma microfields

The effect of electric and magnetic plasma microfields on three-particle electron-ion recombination via the highly excited states of a hydrogen-like ion is studied. It is shown that electric microfields impede this process, and at some electron temperature it ceases for sufficiently high plasma density. Magnetic microfields speed up recombination via low-lying states only negligibly. The rate of such recombination into non-hydrogen-like ion states is comparatively higher than for the equivalent hydrogen-like ion states. Zh. éksp. Teor. Fiz. 114, 1230–1241 (October 1998)     

Loss of electrons from fast heavy structure ions colliding with atoms

Nonperturbative theory is developed for the multiple ionization of fast heavy structure ions colliding with neutral complex atoms. The cross sections for multiple loss of electrons by structure uranium ions U¹⁰⁺ (loss of up to 82 electrons) and U²⁸⁺ (loss of up to 64 electrons) colliding with argon atoms are calculated. The results are compared with available experimental data.     

Laser stimulation of low-temperature dissociative recombination of electrons and oxygen molecular ions

A theory of dissociative recombination of slow electrons and molecular ions in a strong monochromatic light field is developed. The theory takes into account interference between various reaction channels and is constructed in a rigid basis adiabatic with respect to rotation (the approximation of a fixed molecular axis). The mathematical apparatus of the theory is based on the stationary formalism of the matrix of radiation collisions, whose poles correspond to “quasi-energy” states of a composite system. Along with transitions into dissociative configurations, field-induced nonadiabatic transitions into bound intermediate states of valence (non-Rydberg) configurations are considered. As a particular application of the theory, the e^? + O ₂ ⁺ (²Π _g ) → $ O(^{2s_1 + 1} l_1 ) + O(^{2s_2 + 1} l_2 ) A theory of dissociative recombination of slow electrons and molecular ions in a strong monochromatic light field is developed. The theory takes into account interference between various reaction channels and is constructed in a rigid basis adiabatic with respect to rotation (the approximation of a fixed molecular axis). The mathematical apparatus of the theory is based on the stationary formalism of the matrix of radiation collisions, whose poles correspond to “quasi-energy” states of a composite system. Along with transitions into dissociative configurations, field-induced nonadiabatic transitions into bound intermediate states of valence (non-Rydberg) configurations are considered. As a particular application of the theory, the e⁻ + O₂⁺(²Π _g ) → reaction is analyzed. A study of this reaction requires detailed information about the potential curves of the states participating in it with taking into account the external electromagnetic field (l and s are the electronic angular momenta and reaction product spins). For this purpose, the general problem is divided into three stages. At the first stage, the theoretical approach is formulated, and at the second stage, the corresponding potential curves are calculated and the main reaction mechanisms are determined. The third stage should include calculations of the total and differential cross sections. This work is concerned with the first two stages; that is, the adiabatic potential curves of the singlet and triplet dissociative states of the O₂^** oxygen molecule are calculated, a classification of all possible transition types is given, and reaction mechanisms in the presence of monochromatic laser radiation are determined. The frequency regions of external radiation in which these mechanisms are most effective are found. Original Russian Text ? S.O. Adamson, R.J. Buenker, G.V. Golubkov, M.G. Golubkov, A.I. Dement’ev, 2009, published in Khimicheskaya Fizika, 2009, Vol. 28, No. 4, pp. 26–42.     

Spectroscopic study of dissociative recombination between Ar2 + ions and electrons

Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 49, No. 3, pp. 407–412, September, 1988.     

Simultaneous jumps in two two-level atoms

We demonstrate the importance of collective behaviour in two identical two-level atoms. When the atoms become very close together a cascade three-level atom analysis can be adopted to show the increasing possibility of simultaneous jumps. Due to the dipole-dipole interaction the intermediate one-atom excited state is detuned by a large amount when the atoms are close together but leaving the upper two-atom excited state in two-photon resonance. The relative importance of multiple jumps compared with stepwise independent jumps is then changed dramatically.     

The dissociative recombination of HeNe+ ions with electrons: The partial rate constants for the formation of atoms in the 2p 53p configuration

A simple experiment transparent for interpretation is presented in which afterglow of a discharge in helium with a small admixture of neon was studied. The intensities of the spectral lines of the Ne* atom at the stage of plasma decay were analyzed to find the conditions under which the dissociative recombination of heteronuclear ions HeNe⁺ + e ?? He + Ne* played a predominant role in the formation of part of the after-glow spectrum. The absolute values of partial coefficients responsible for the formation of excited neon atoms in the 2p ⁵3p configuration were determined.     

Berry phase effects in two-level and three-level atoms

Group-theoretical methods are developed for treating Berry phase effects, which are related to Cartan subalgebra. The theory is applied to two-level and three-level atoms interacting with perturbations that are described by the SU(2) or SU(3) algebra. By using fiber-bundle theories, it is found that a time development operator that depends on Cartan group generators can represent a fiber while a time development operator that depends on other generators of the group represents the base of the quantum manifold. The total time development operator is obtained by multiplication of these two parts and the fiber-bundle theory is applied for calculating Berry phase effects. Explicit expressions for Berry phases are obtained under the adiabatic approximation.     

Elastic scattering of electrons by metastable hydrogen atoms in the presence of a resonant laser field

Within the framework of the rotating wave approximation the elastic scattering of electrons by metastable 2s state of hydrogen atoms is studied in the presence of a resonant laser field. The frequency of the circularly polarized laser field is chosen to match the 2s-3p transition frequency in the hydrogen atom. Variation of the cross section with laser intensity and with incident electron energy (50-150 eV) is investigated. Received: 18 July 1997 / Received in final form: 5 December 1997 / Accepted: 19 January 1998     

Three-body recombination in bose gases with large scattering length

An effective field theory for the three-body system with large scattering length is applied to three-body recombination to a weakly bound s-wave state in a Bose gas. Our model independent analysis demonstrates that the three-body recombination constant alpha is not universal, but can take any value between zero and 67.9Planck's over 2pia(4)/m, where a is the scattering length. Other low-energy three-body observables can be predicted in terms of a and alpha. Near a Feshbach resonance, alpha should oscillate between those limits as the magnetic field B approaches the point where a-->infinity. In any interval of B over which a increases by a factor of 22.7, alpha should have a zero.     

Anomalous Doppler-effect and polariton-mediated cooling of two-level atoms

We consider an atom moving in a near resonant laser field with its dipole strongly coupled to a resonator field mode. As compared to the standard Doppler shift, we find a substantially different and counterintuitive linear velocity dependence of the light scattering properties. The mechanical force of the laser field exhibits strong velocity selectivity at a polariton resonance, which gives rise to an enhanced friction force and Doppler cooling even in the directions perpendicular to the resonator axis. This effect allows for sub-Doppler cooling of atoms even with a nondegenerate ground state.     

Dissociative recombination of electrons and O 2 + molecular ions in the field of intense visible laser radiation

We analyze the low-temperature dissociative recombination reaction e ^?+O ₂ ⁺ → O(¹ D)+O(³ P) in the field of visible monochromatic laser radiation. The analysis is performed in terms of the multichannel quantum defect theory using the stationary formalism of the radiative collision matrix. We calculate the dependences of the reaction cross section on the incident electron energy, the external electromagnetic field strength and frequency, and also the angle between the directions of the electron beam and the electric vector for linearly polarized radiation. The cross section is shown to increase by several orders of magnitude for a certain choice of these parameters, suggesting the possible laser stimulation of this reaction.