Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

Optics and Spectroscopy

Diffusion ionization of the Rydberg diatomic quasi-molecular complex formed upon collisions of rubidium atoms

Nikolai N. Bezuglov, V. M. Borodin, V. B. Grushevskii, Andrey N. Klyucharev, K. Miculis, F. Fuzo, M. Allegrini

Published Oct 1, 2003• 8 citations
Publisher

Abstract

The problem of impact ionization of two Rb atoms, one of which belongs to the Rydberg P series and the other of which is in the ground state, is studied and solved with the use of the methods of stochastic dynamics for description of the path instability of a Rydberg electron in a collision diatomic complex. The actual potential of the atomic framework was taken into account in terms of the single-channel quantum-defect method, whose accuracy was demonstrated on the example of determination of the photoionization cross sections in the quasi-classical approximation. A representation of the effective average lifetime of an external electron in the bound state that takes into account both the diffusion migration within the Coulomb crowding of the potential energy curves for the quasi-molecular complex and the direct quantum autoionization is obtained in analytical form. It is shown that the rate constants of diffusion collisional ionization calculated by us are in good agreement with the experimental data.

DOI
10.1134/1.1621434

Related papers

Dynamic resonances in the autoionization Rydberg states of atomic systems

Nikolai N. Bezuglov, Gennady V. Golubkov, Andrey N. Klyucharev

Contemporary views on the formation of dynamic nonlinear resonances in isolated intermediate Rydberg quasi-molecular complexes formed by a single elementary act upon the slow collision highly excited atoms are discussed. A relation between the emergence of dynamic resonance and the quasi-intersection of atomic terms is revealed in the quasi-classical approximation. Relationships between the widths of dynamic resonances and the dipole matrix element leading to the corresponding quasi-intersections are determined. The physical reasons for the dynamic chaos regime are formulated. A quasi-classical statistical description is given of the diffusion ionization of an atomic complex with a dense network of quasi-intersections of terms. Development of the stochastic instability of the Rydberg electron trajectories due charge exchange inside the collision complex is considered. The effect the narrowing region of stochastic motion has when passing through the Coulomb convergence of the levels with a simultaneous drop in the ionization rate of quasi-molecular systems is predicted for external statistical magnetic and electric fields under conditions of Förster resonance.

Russian Journal of Physical Chemistry A•Oct 9, 2014•2 citations

Analysis of Fokker-Planck type stochastic equations with variable boundary conditions in an elementary process of collisional ionization

Nikolai N. Bezuglov, V. M. Borodin, Andrey K. Kazansky +3 more

The diffusion model of ionization of Rydberg atoms in single collisions is formulated. The solution of kinetic equations describing nonstationary diffusion processes is discussed. Methods of analytical calculation of the effective times for the development of ionization in phase regions with moving boundaries are presented. An analytical method, going back to Weisskopf, for determining the corresponding cross sections for impact ionization in the adiabatic approximation is described. A numerical scheme for solving problems of stochastic movement of a Rydberg electron inside a Coulomb condensation of levels under conditions of time-variable ionization boundaries and region of development of stochastic instability is developed.

Optics and Spectroscopy•Jul 1, 2001•23 citations

Collisional and thermal ionization of sodium Rydberg atoms: II. Theory fornS,nP andnD states withn= 5–25

K. Miculis, Ilya I. Beterov, Nikolai N. Bezuglov +4 more

A stochastic model of associative ionization in collisions of Rydberg atoms with ground-state atoms is presented. The conventional Duman–Shmatov–Mihajlov–Janev (DSMJ) model treats the ionization as excitation of Rydberg electron to the continuum by the electric-dipole field generated by exchange interaction within the quasi-molecular ion. The stochastic model essentially extends this treatment by taking into account redistribution of population over a range of Rydberg states prior to ionization, which is caused by non-adiabatic processes in overlapping multiple level crossings of quasi-molecular Rydberg states. The redistribution is modelled as diffusion of electrons in the Rydberg energy spectrum using a Fokker–Planck-type equation. The process of l -mixing of Rydberg states at large internuclear distances and twisting of the collision trajectories on attractive potentials are taken into account. The choice of the collision velocity distribution is also shown to be important. Associative ionization rates have been calculated for Na**( nl ) + Na collisions with n = 5–25 and l = 0, 1, 2, and compared with the available experimental data and the calculations performed using the nonlinear DSMJ model. At relatively low n the stochastic model yields a substantially better agreement with the experimental data than the DSMJ model, while the results of both models converge at large n .

Journal of Physics B Atomic Molecular and Optical Physics•May 26, 2005•34 citations

Impulse-approximation analysis of collisions between Rydberg and ground-state rubidium atoms at thermal energies

I. I. Fabrikant

The impulse approximation for the Rydberg atom-atom collisions is analyzed on the basis of the Faddeev equations. A modified expression is derived for the cross sections, including the interference between the Rydberg-electron--perturber scattering and the ion-core--perturber scattering. This expression is used for the calculations of the collisional quenching and elastic scattering in Rb(nS)-Rb and Rb(nP)-Rb collisions. We use the electron-Rb scattering phase shifts obtained from ab initio close-coupling calculations and their extrapolation, applying the modified effective-range theory. Our results show that the impulse approximation agrees with the experimental data for the quenching cross sections at n>20 but underestimates the quenching cross sections at lower n. The position of the maximum of the cross section is in good agreement with experimental data. We also obtain reasonable results for the elastic cross section at n>20, but for the lower n the results are too large. The interference effect plays a minor role in the process, which means that simultaneous electron-perturber and ion-perturber interaction is unlikely.

Physical Review A•May 1, 1992•17 citations

Inelastic processes in slow collisions of Rydberg atoms with atoms in the ground state

D. B. Khrebtukov

This dissertation deals with thermal collisions of highly excited (Rydberg) atoms with atoms in the ground state. The inelastic processes in these collisions manifest themselves mainly in broadening of Rydberg spectral lines. Advancements in tunable laser techniques allowed observation of the ion-pair formation in such collisions as well. Theoretical treatments of these collisions can be separated in two groups according to the principal quantum number n of the Rydberg atom: impulse approximation $(n\ge30),$ and adiabatic approximation $(n\le20).$ Both approaches are presented in application to spectral line broadening. The off-shell modification of the impulse approximation is developed. The pseudopotentials for singlet and triplet electron scattering from Rb and Cs are re-constructed from the phase shift data. These potentials are used to calculate the off-shell amplitudes, which are employed to obtain broadening cross sections. The taking into account of the off-shell effects is shown to improve the agreement with the experiment in the intermediate region of principal quantum number $20 < n < 30.$ The adiabatic approximation in the framework of Borodin-Kazansky theory is improved to include the exact Coulomb Green's function and the final radius of the ground state atom. The adiabatic theory explains the oscillations with n in the experimental broadening cross sections. The adiabatic theory is developed for the ion-pair formation. The zero-range-potential-Coulomb-field model is employed to generate realistic energy curves. The model allows exact numerical solution, which is used to verify the analytical theory that is set forth to describe the non-adiabatic transitions at large internuclear distances. Adiabatic calculations rely on the complex plane technique that requires the analytical continuation of the energy curves in the complex plane of parameters. Development of the algorithms for the continuation of Mathieu and Whittaker's functions, used in these calculations, constitutes an important methodological achievement of this work. Although all applications of the theories are worked out for alkali-metal atoms, the results can be applied to other atomic species as well.

•Jan 1, 1995•0 citations

The study of collisional ionization properties of Rydberg Cs atoms with CCl 4 molecules

Chun Li

In order to explain some characteristics discovered in the experimental study of the collisional ionization of Rydberg Cs atoms with CCl 4 molecules, two corrections were made to the quasi free electron mode, commonly used to describe the collsional ionization of Rydberg atoms with molecules:(1)the influence of the core and the quantum defect of Rydberg atom were taken into account;(2)the separation probability of the product ion pair was calculated. With this corrected model, a theoretical result in good agreement with our experiment measurements was obtained. A comparison with another reported experimental result was also made.

Chinese journal of atomic and molecular physics•Jan 1, 1999•0 citations
The problem of impact ionization of two Rb atoms, one of which belongs to the Rydberg P series and the other of which is in the ground state, is studied and solved with the use of the methods of stochastic dynamics for description of the path instability of a Rydberg electron in a collision diatomic complex. The actual potential of the atomic framework was taken into account in terms of the single-channel quantum-defect method, whose accuracy was demonstrated on the example of determination of the photoionization cross sections in the quasi-classical approximation. A representation of the effective average lifetime of an external electron in the bound state that takes into account both the diffusion migration within the Coulomb crowding of the potential energy curves for the quasi-molecular complex and the direct quantum autoionization is obtained in analytical form. It is shown that the rate constants of diffusion collisional ionization calculated by us are in good agreement with the experimental data.
Contemporary views on the formation of dynamic nonlinear resonances in isolated intermediate Rydberg quasi-molecular complexes formed by a single elementary act upon the slow collision highly excited atoms are discussed. A relation between the emergence of dynamic resonance and the quasi-intersection of atomic terms is revealed in the quasi-classical approximation. Relationships between the widths of dynamic resonances and the dipole matrix element leading to the corresponding quasi-intersections are determined. The physical reasons for the dynamic chaos regime are formulated. A quasi-classical statistical description is given of the diffusion ionization of an atomic complex with a dense network of quasi-intersections of terms. Development of the stochastic instability of the Rydberg electron trajectories due charge exchange inside the collision complex is considered. The effect the narrowing region of stochastic motion has when passing through the Coulomb convergence of the levels with a simultaneous drop in the ionization rate of quasi-molecular systems is predicted for external statistical magnetic and electric fields under conditions of Förster resonance.
The diffusion model of ionization of Rydberg atoms in single collisions is formulated. The solution of kinetic equations describing nonstationary diffusion processes is discussed. Methods of analytical calculation of the effective times for the development of ionization in phase regions with moving boundaries are presented. An analytical method, going back to Weisskopf, for determining the corresponding cross sections for impact ionization in the adiabatic approximation is described. A numerical scheme for solving problems of stochastic movement of a Rydberg electron inside a Coulomb condensation of levels under conditions of time-variable ionization boundaries and region of development of stochastic instability is developed.
A stochastic model of associative ionization in collisions of Rydberg atoms with ground-state atoms is presented. The conventional Duman–Shmatov–Mihajlov–Janev (DSMJ) model treats the ionization as excitation of Rydberg electron to the continuum by the electric-dipole field generated by exchange interaction within the quasi-molecular ion. The stochastic model essentially extends this treatment by taking into account redistribution of population over a range of Rydberg states prior to ionization, which is caused by non-adiabatic processes in overlapping multiple level crossings of quasi-molecular Rydberg states. The redistribution is modelled as diffusion of electrons in the Rydberg energy spectrum using a Fokker–Planck-type equation. The process of l -mixing of Rydberg states at large internuclear distances and twisting of the collision trajectories on attractive potentials are taken into account. The choice of the collision velocity distribution is also shown to be important. Associative ionization rates have been calculated for Na**( nl ) + Na collisions with n = 5–25 and l = 0, 1, 2, and compared with the available experimental data and the calculations performed using the nonlinear DSMJ model. At relatively low n the stochastic model yields a substantially better agreement with the experimental data than the DSMJ model, while the results of both models converge at large n .
The impulse approximation for the Rydberg atom-atom collisions is analyzed on the basis of the Faddeev equations. A modified expression is derived for the cross sections, including the interference between the Rydberg-electron--perturber scattering and the ion-core--perturber scattering. This expression is used for the calculations of the collisional quenching and elastic scattering in Rb(nS)-Rb and Rb(nP)-Rb collisions. We use the electron-Rb scattering phase shifts obtained from ab initio close-coupling calculations and their extrapolation, applying the modified effective-range theory. Our results show that the impulse approximation agrees with the experimental data for the quenching cross sections at n>20 but underestimates the quenching cross sections at lower n. The position of the maximum of the cross section is in good agreement with experimental data. We also obtain reasonable results for the elastic cross section at n>20, but for the lower n the results are too large. The interference effect plays a minor role in the process, which means that simultaneous electron-perturber and ion-perturber interaction is unlikely.
This dissertation deals with thermal collisions of highly excited (Rydberg) atoms with atoms in the ground state. The inelastic processes in these collisions manifest themselves mainly in broadening of Rydberg spectral lines. Advancements in tunable laser techniques allowed observation of the ion-pair formation in such collisions as well. Theoretical treatments of these collisions can be separated in two groups according to the principal quantum number n of the Rydberg atom: impulse approximation (n≥30),(n\ge30),(n≥30), and adiabatic approximation (n≤20).(n\le20).(n≤20). Both approaches are presented in application to spectral line broadening. The off-shell modification of the impulse approximation is developed. The pseudopotentials for singlet and triplet electron scattering from Rb and Cs are re-constructed from the phase shift data. These potentials are used to calculate the off-shell amplitudes, which are employed to obtain broadening cross sections. The taking into account of the off-shell effects is shown to improve the agreement with the experiment in the intermediate region of principal quantum number 20<n<30.20 < n < 30.20<n<30. The adiabatic approximation in the framework of Borodin-Kazansky theory is improved to include the exact Coulomb Green's function and the final radius of the ground state atom. The adiabatic theory explains the oscillations with n in the experimental broadening cross sections. The adiabatic theory is developed for the ion-pair formation. The zero-range-potential-Coulomb-field model is employed to generate realistic energy curves. The model allows exact numerical solution, which is used to verify the analytical theory that is set forth to describe the non-adiabatic transitions at large internuclear distances. Adiabatic calculations rely on the complex plane technique that requires the analytical continuation of the energy curves in the complex plane of parameters. Development of the algorithms for the continuation of Mathieu and Whittaker's functions, used in these calculations, constitutes an important methodological achievement of this work. Although all applications of the theories are worked out for alkali-metal atoms, the results can be applied to other atomic species as well.
In order to explain some characteristics discovered in the experimental study of the collisional ionization of Rydberg Cs atoms with CCl 4 molecules, two corrections were made to the quasi free electron mode, commonly used to describe the collsional ionization of Rydberg atoms with molecules:(1)the influence of the core and the quantum defect of Rydberg atom were taken into account;(2)the separation probability of the product ion pair was calculated. With this corrected model, a theoretical result in good agreement with our experiment measurements was obtained. A comparison with another reported experimental result was also made.