Shift of Cl Kα and Kβ Lines in Laser Produced Dense Plasmas

The features of chlorine K‐lines have been investigated to develop X‐ray probes for Compton scattering on warm dense plasmas. The shapes of these spectral lines have been studied at different laser energies by irradiation of thin saran foils by an intense ultra‐short‐pulse laser beam. The observed positions of Kα and Kβ lines undergo a red shift due to a laser induced plasma environment. With increasing intensities the shift changes direction and turns into a blue shift caused by a higher contribution of K‐transitions occuring in further excited or ionized atoms. A theoretical approach based on the self‐consistent ion sphere model is outlined to describe this inversion. Plasma polarization effects are taken into account as well as different ionization stages of the X‐ray emitter within a warm dense plasma. Calculations using an improved ion sphere ansatz show good agreement with observations of the line shifts. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)