Eur. Phys. J. D 47, 27-31 (2008)
https://doi.org/10.1140/epjd/e2008-00032-4

Plasma screening within Rydberg atoms in circular states

¹ School of Physics, Georgia Institute of Technology, Atlanta, GA, 30332, USA
² Physics Department, 206 Allison Lab., Auburn University, Auburn, AL, 36849, USA

Corresponding author: ^a goks@physics.auburn.edu

Received: 18 June 2007
Revised: 26 January 2008
Published online: 29 February 2008

Abstract

A Rydberg atom embedded in a plasma can experience penetration by slowly moving electrons within its volume. The original pure Coulomb potential must now be replaced by a screened Coulomb potential which contains either a screening length R_s or a screening factor A = R_s^-1 . For any given discrete energy level, there is a Critical Screening Factor (CSF) A_c beyond which the energy level disappears (by merging into the continuum). Analytical results are obtained for the classical dependence of the energy on the screening factor, for the CSF, and for the critical radius of the electron orbit for Circular Rydberg States (CRS) in this screened Rydberg atom. The results are derived for any general form of the screened Coulomb potential and are applied to the particular case of the Debye potential. We also show that CRS can temporarily exist above the ionization threshold and are therefore the classical counterparts of quantal discrete states embedded into continuum. The results are significant not only to Rydberg plasmas, but also to fusion plasmas, where Rydberg states of multi-charged hydrogen-like ions result from charge exchange with hydrogen or deuterium atoms, as well as to dusty/complex plasmas.