Demonstration of quasiresonant x-ray photoexcitation in a laser-created plasma

Resonant photoexcitation in a two-component plasma is demonstrated for the first time in the x-ray range. The 1s-3p resonance line of Al xiii at 6.053 A{} is used to pump the 2p*{(}¹S₀)-2p⁵3d (³{D}₁$) line of Sr xxix at 6.059 {}. Absorption of the aluminum pump line by the strontium plasma is shown unambiguously. The resulting increase in the x-ray fluorescence intensity of the pumped level is measured in a time-resolved experiment.