Possibility of using metastable heliumlike ions in generation of ultrasoft x-ray stimulated radiation

An experimental investigation demonstrated that, in principle, it should be possible to establish a population inversion needed in an x-ray laser by accumulation of metastable heliumlike ions (Li II*, Be III*, B IV*, B V*, etc.) in the 2s state and rapid transfer of these ions to the 2p state. A dense decaying plasma produced by a high-current discharge pulse in lithium vapor was the source of metastable ions. A study was made of the composition, density, and velocity of ions leaving the discharge chamber. X-ray luminescence was due to the 1s2p ¹P₁→1s^{2 1}S₀(λ = 19.9 nm) transition pumped by the 1s2s ¹S₀→1s2p¹P₁(λ = 962 nm) radiation produced by an IFP–5000 xenon pulse-discharge lamp.