Eur. Phys. J. D 19, 65-72 (2002)
https://doi.org/10.1140/epjd/e20020056

An analytic collisional-radiative model incorporating non-LTE and optical depth effects

Instituto de Física Arroyo Seco (IFAS), Universidad Nacional del Centro Pinto 399, B7000GHG, Tandil and CONICET, Argentina

Corresponding authors: ^a juanp@exa.unicen.edu.ar - ^b hdirocco@exa.unicen.edu.ar

Received: 12 June 2001
Revised: 24 October 2001
Published online: 15 April 2002

Abstract

In this paper we analyze the variations in line intensities ratios due to a non-equilibrium situation and to optical depth effects. A four level model is proposed and the two particular situations for the possible transitions are considered. Electron density and temperature as well as the source thickness are used as independent parameters to find out in which way and extent they modify the ratios of levels populations compared with the ideal case of an equilibrium state and optically thin source. Accordingly with the ion of interest, electron temperatures ranging from I/20 to I/7 eV (I being the ionization energy), whereas electron densities in the interval from 10¹⁴ to  cm^-3 will be considered. These ranges are of special interest for diverse applications such as LIBS and measurement of transition probabilities. Some results are presented for real ions and a new expression for the escape factor is also proposed for general plasma conditions.