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 i i, O i i i, C i i i, and N i i i ions are reported. Ions are produced due to optical field ionization of ${\mathrm{O}}_2$, ${\mathrm{CO}}_2$, and ${\mathrm{N}}_2$ gases in an intense Ti:sapphire laser field. Amplificaiton on the 2p3s${(}^3$P)-2${\mathit{p}}^2$ ${(}^3$P) transition (λ=374.12 Å) in O i i i ions and on the 2${\mathit{p}}^2$3s${(}^2$P)-2${\mathit{p}}^3$ ${(}^2$D) transition (λ=616.56 Å) in O i i ions has been observed.