Inner-shell satellite transitions in dense short pulse plasmas

Soft x-ray spectra originating from dense plasmas, generated by a laser irradiating a solid target with ns- and fs-laser pulses, have been obtained with simultaneous high spectral (λ/δλ 10 000) and spatial resolution (δx ≈ 10 μm). Interesting structure of the He-like resonance line together with strong emission of the Li-like n = 2 satellites have been observed very close to the target surface. We show here that the resonance line structure is strongly influenced by higher order satellites of the type 1s2nl'-1s2lnl' which overlap for n > 2. For plasmas created with short pulse duration lasers there are high density and low temperature regions near the target that give rise to three body recombination into Rydberg satellite levels leading to substantial intensity at the position of the resonance transition. Atomic data necessary for spectra simulations have been calculated with inclusion of configuration interaction and relativistic effects and these results are cross-checked with other calculational methods. Time-dependent simulations of the spectra including the effects of optical thickness, energetic electrons and numerous high order Rydberg satellites (up to n = 7) are found to be in good agreement with experimental data.