A. Bourdon et al., IONIZATION AND RECOMBINATION RATES OF ATOMIC OXYGEN IN HIGH-TEMPERATURE AIR PLASMA FLOWS, Physical review. E, Statistical physics, plasmas, fluids, and related interdisciplinary topics, 57(4), 1998, pp. 4684-4692
A nonlinear time-dependent collisional-radiative model for atomic oxyg
en is presented. Effective ionization and three-body recombination rat
e coefficients are calculated for either optically thin or thick plasm
as where 10(18) m(-3)less than or equal to n(e) less than or equal to
10(21) m(-3) and 8000 K less than or equal to T-e less than or equal t
o 20 000 K. In order to implement these coefficients easily in plasma
flow codes, simple analytical expressions are proposed. Significant di
screpancies with existing literature values are pointed out and discus
sed. The time-dependent approach confirms the importance of a quasiste
ady-state condition to derive meaningful rate coefficients. Therefore
the relaxation time necessary for the system to reach a quasi-steady-s
tate limits the validity of the rate coefficients determined in this s
tudy. In optically thick cases, this relaxation time in either recombi
ning or ionizing plasmas depends weakly on the electron temperature bu
t strongly increases as the electron number density decreases. In opti
cally thin cases, it is more difficult to derive general results since
the relaxation time depends on the electron temperature, on densities
, but also on the initial distribution on atomic levels.