Temperature and ionization balance dependence of O VII line ratios

The intensity ratio of n = 2 → 1 triplet lines to the resonance line of O VII can provide information on x-ray radiative-transfer effects and departures from ionization equilibrium in the solar corona. This ratio, commonly designated G, is calculated theoretically with detailed attention to all important atomic processes. For a steady-state plasma G = 0.8 +- 0.1 over a 0.6 to x 106K range of temperature. On the other hand, strong variations of G are found for plasmas which are out of ionization equilibrium. Collisional and recombination population rates are tabulated for the 2 1P and 2 3S + 2 3P levels of O VII. 1 figure, 2 tables