Population inversion of levels of Al XII ions in a recombining laser plasma

An experimental investigation was made of the expansion of an aluminum laser plasma into vacuum. X-ray spectral methods were used to determine the plasma parameters (temperature, density, and ionization state) and the ion distribution in terms of excited levels. A qualitative and quantitative interpretation of the experimental data is given and an estimate is obtained for the gains due to far ultraviolet (λ = 76–280 Å) transitions in the Al XII ion.