Dresden 2011 – scientific programme
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A: Fachverband Atomphysik
A 1: Interaction with VUV and X-ray light (FEL) I
A 1.2: Invited Talk
Monday, March 14, 2011, 11:00–11:30, BAR 205
X-FEL induced multi-photon processes — •Bertold Krässig — Argonne National Laboratory, Argonne, IL 60439, USA
The opening of the world’s first X-ray Free Electron Laser (X-FEL), the Linac Coherent Light Source (LCLS) at the SLAC National Accelerator Laboratory, marked an important milestone in the effort to probe matter at the length and time scales of atoms and molecules. Never before has it been possible to direct hundreds of x-ray photons (800 eV-8000 eV) onto every single atom at the focus of the x-ray beam during a single pulse lasting 200 fs or less. In this talk I will present results of some of the first experiments carried out at the LCLS with the goal of exploring multiphoton processes in atoms at short wavelengths. The atom of choice in these experiment was neon. We found the target atoms to become continually altered during a single x-ray pulse by absorbing multiple photons sequentially, in some cases removing all 8 valence electrons if the photon energy is below the 1s ionization threshold, or all 10 electrons if the photon energy is above the 1s ionization threshold of Ne9+. At sufficiently high beam intensities and energies above the 1s ionization thresholds, both 1s electrons can be sequentially removed before Auger decay occurs. Such creation of a hollow atom leads to a temporary reduction in the probability for photoabsorption, and the reduction becomes the more prominent the longer the lifetime of the hollow atom state. Our results demonstrate how different, and in many ways complementary, X-FEL sources are as a research tool compared to traditional synchrotron radiation facilities.