The influence of (n - n^′)-mixing processes in He^* (n) + He (1 s²) collisions on He^* (n) atoms' populations in weakly ionized helium plasmas

Abstract

The results of semi-classical calculations of rate coefficients of (n - n′)-mixing processes due to collisions of Rydberg atoms He* (n) with He (1 s2) atoms are presented. It is assumed that these processes are caused by the resonant energy exchange within the electron component of He* (n) + He collision system. The method is realized through the numerical simulation of the (n - n′)-mixing processes, and is applied for calculations of the corresponding rate coefficients. The calculations are performed for the principal quantum numbers n, n′ in ranges 4 ≤ n < n′ ≤ 10, and the atom and electron temperatures, Ta, Te, in domains 5000 K ≤ Ta ≤ Te ≤ 20 000 K. It is shown that the (n - n′)-mixing processes can significantly influence the populations of Rydberg atoms in non-equilibrium weakly ionized helium plasmas with ionization degree ∼ 10- 4. Therefore, these processes have to be included in the appropriate models of such plasmas. © 2007 Elsevier Ltd. All rights reserved.