Ab initio Al XI and S XIV spectra. Transient population inversions in laser-produced plasmas

Ab initio Al XI and S XIV wavelengths below 400 AA involving transitions between 1s 2 nl 2 L J levels up to n=7 are reported. The accuracy is better than 1% in all cases where existing data allow for comparison. Corresponding transition probabilities are given. A time-dependent collisional radiative model is used to calculate the populations of Al 10+ states in laser-produced plasmas. Population inversions occur between n=5, n=4 and n=3 levels at well defined times of the plasma recombination phase. The conditions of validity of the model are discussed, particularly with regard to the optical depth of the plasma for each resonance line, and conclusions are drawn from an appropriate criterion.