Soft-x-ray lasing to the ground states in low-charged oxygen ions

Optimal schemes for the creation of a transient population inversion between the ground and excited states of an ion in a subpicosecond-pulse laser-produced plasma are discussed. First results on experimental investigations of possible amplification in the soft-x-ray spectral region on transitions to the gorund states in O ii, O iii, C iii, and N iii ions are reported. Ions are produced due to optical field ionization of O₂, CO₂, and N₂ gases in an intense Ti:sapphire laser field. Amplificaiton on the 2p3s(³P)-2p²{(}³P) transition (λ=374.12 ) in O iii ions and on the 2{p}²$3s${(}²$P)-2${p}³(²D) transition ({λ}=616.56 {}) in O ii ions has been observed.