SACLA: new opportunities for atomic, molecular, and cluster science with XFEL

Abstract

X-ray free-electron lasers (XFELs) provide extremely intense femtosecond x-ray pulses that promise access to high-resolution structure determination, while outrunning any radiation damage. To achieve this goal, however, requires the ability to describe the dynamical behavior of heavy atoms in high-intensity x-ray pulses. In early 2012, a new XFEL facility, the SPring-8 Angstrom Compact free electron LAser (SACLA), started user operation in Japan [1,2]. We set up the program to investigate the dynamical behavior of heavy atoms as an isolated atom, in the molecule, and in the cluster, with SACLA. At 5.5 keV, with the fluence of 50 μJ/μm2, we could identify that Xen+ with n up to 26 is produced (Fig. 1), evidencing the occurrence of deep inner-shell ionization and sequential electronic decay cycles repeated multiple times in the heavy atom within the XFEL pulse of < 20 fs (Fig. 2) [3]. Reducing the photon energy to 5 keV, with the fluence of 50 μJ/μm2, we could identify the occurrence of resonance-enabled x-ray multiple ionization [4].