Soft X-ray population inversion in laser plasmas by resonant photoexcitation and photon-assisted processes

In this paper, the results of studies on soft X-ray population inversion by the resonant photoexcitation process are presented. The experimental studies in highly ionized multicomponent plasmas produced by high power glass laser indicate large population inversion densities at wavelengths
\lsim 130
Å. Intensity inversions of resonance lines from the
n = 3
and
n = 4
levels of Mg
¹¹⁺
ions at electron densities as high as 10
²⁰
cm
^-3
have been observed, indicating that gains of
\sim 5-10
cm
^-1
have been achieved. These results and other photon-assisted soft X-ray population inversion schemes in inhomogeneous plasmas are discussed.