High-resolution x-ray saturation spectroscopy of krypton L-shell autoionizing transitions

The achievement of controlled saturation with high spectral resolution (~2–3 eV) provides a refined diagnostic for the quantitative study of the propagation of intense beams of x-rays. This work demonstrates the characteristics of saturation spectroscopy with an analysis of Kr(L) autoionizing transitions at ħω = 1652 eV. The data include single-pulse x-ray spatial morphologies, corresponding Thomson images of the electron density, and spatially resolved transversely observed x-ray spectra that are recorded longitudinally along the direction of propagation of a Kr26+ (λ26 = 7.504 A) beam in a Kr n cluster medium. The results reveal the complex interactions associated with the propagation of the 7.504 A x-ray beam and, based on sets of quantitative criteria, attribute the observed behavior to the saturation of 2p → 3d transitions to autoionizing states of Kr15+ and Kr16+ ionic species.