Absorption spectroscopy of the K-shell Rydberg series in a Mg laser-produced plasma

The K-shell resonance and dielectronic satellite lines of Mg XI through Mg VIII have been observed in absorption in a near-LTE, radiatively-heated, laser-produced plasma. Measurements of the absorption of 1.3-1.7 keV X-rays from a Dy backlighter layer by 1-2, 1-3 and 1-4 transitions have been made with high spectral resolution. Radiative hydrocode simulations and detailed atomic physics calculations describe correctly the experimental results, except for the 1s2-1s2p resonance line of Mg XI which is always observed in emission. Resonance fluorescence resulting from a collisional-radiative cascade from the Mg XI 1s3p level photopumped by the strong 3d-4f transition arrays of Dy could be the source of the observed emission.