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 […]