M-shell Resolved High-Resolution X-Ray Spectroscopic Study of Transient Matter Evolution Driven by Hot Electrons in kJ-Laser Produced Plasmas

Hot electrons represent a key subject for high intensity laser produced plasmas and atomic physics. Simulations of the radiative properties indicate a high sensitivity to hot electrons, that in turn provides the possibility for their detailed characterization by high-resolution spectroscopic methods. Of particular interest is X-ray spectroscopy due to reduced photo-absorption in dense matter and their efficient generation by hot electrons (inner-shell ionization/excitation). Here, we report on an experimental campaign conducted at the ns, kJ laser facility PALS at Prague in Czech Republic. Thin copper foils have been irradiated with 1 omega pulses. Two spherically bent quartz Bragg crystal spectrometers with high spectral (λ/Δλ > 5000) and spatial resolutions (Δx = 30 μm) have been set up simultaneously to achieve a high level of confidence for the complex Kα emission group. In particular, this group, which shows a strong overlap between lines, can be resolved in several substructures. Furthermore, an emission on the red wing of the Kα₂ transition (λ=1.5444 A) could be identified with Hartree-Fock atomic structure calculations. We discuss possible implications for the analysis of noN_equilibrium phenomena and present first simulations. (authors)