Collisional and thermal ionization of sodium Rydberg atoms: II. Theory for nS, nP and nD states with n = 5-25

K. Miculis*, I. I. Beterov, N. N. Bezuglov, I. I. Ryabtsev, D. B. Tretyakov, Aigars Ekers, A. N. Klucharev

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

25 Scopus citations

Abstract

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.

Original languageEnglish (US)
Pages (from-to)1811-1831
Number of pages21
JournalJournal of Physics B: Atomic, Molecular and Optical Physics
Volume38
Issue number11
DOIs
StatePublished - Jun 14 2005

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics
  • Condensed Matter Physics

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