Experimental evidence for soft x-ray population inversion by resonant photoexcitation in multicomponent laser plasmas

High-intensity laser-plasma experiments conducted on targets consisting of carbon and magnesium indicate population inversion in Mg+10 and Mg+11 ions at wavelengths of ∼100 Å. The results indicate that soft x-ray population inversion has been achieved, for the first time, by resonant photoexcitation. By this process, intensity inversions of the hydrogenic resonance lines from n=3 and n=4 are observed at electron densities as high as 1020 cm−3.