Phys.org July 29, 2024
To understand its electronic structure and structure upon irradiation with strong laser pulses, an international team of researchers (Germany, Slovenia, Sweden, Switzerland, Poland, USA – University of Washington) simultaneously created and characterized warm dense copper over a large irradiation intensity range. An absorption peak below the L edge appeared from transient depletion of the 3d band. The peak shifted to lower energy with increasing intensity, indicating the movement of the 3d band upon strong X-ray excitation. At higher intensities, substantial ionization and collisions led to the transition from reverse saturable absorption to saturable absorption of the X-ray free-electron laser pulse. They used theoretical calculations to combine a model based on kinetic Boltzmann equations with finite-temperature real-space density-functional theory to interpret these observations. According to the researchers the results could be used to benchmark non-equilibrium models of electronic structure in warm dense matter… read more. Open Access TECHNICAL ARTICLEÂ
Sketch of the experimental setup and results. Credit: European XFEL; Laurent Mercadier.