Abstract
Atomic inner-shell relaxation dynamics were measured at the free-electron laser in Hamburg, FLASH, delivering 92 eV pulses. The decay of 4d core holes created in xenon was followed by detection of ion charge states after illumination with delayed 400 nm laser pulses. A timing jitter of the order of several hundred femtoseconds between laser- and accelerator-pulses was compensated for by a simultaneous delay measurement in a single-shot x-ray/laser cross-correlator. After sorting of the tagged spectra according to the measured delays, a temporal resolution equivalent to the pulse duration of the optical laser could be established. While results on ion charge states up to Xe4+ are compatible with a previous study using a high-harmonic soft x-ray source, a new relaxation pathway is opened by the nonlinear excitation of xenon atoms in the intense free-electron laser light field, leading to the formation of Xe5+.
Highlights
Linear Accelerator Center (SLAC) [18], where the timing information was deduced from electro-optical sampling (EOS) [19] of the relativistic electron bunches
In a previous work we introduced a single-shot cross-correlator that directly compares the arrival times of visible and soft x-ray pulses at the experimental end-station of FLASH [20], removing timing uncertainties connected with the x-ray generation and the beam transport from the undulator to the experiment
Electron relaxation in Xe atoms was initiated by excitation of the 4d-shell with 92 eV soft x-ray pulses of the free-electron-laser FLASH
Summary
Linear Accelerator Center (SLAC) [18], where the timing information was deduced from electro-optical sampling (EOS) [19] of the relativistic electron bunches. Precise knowledge of the very short Xe-NOO Auger decay time constant (6.0 ± 0.7 fs) allows us to determine the achievable resolution with high precision. While in this case atomic dynamics mainly serves as a standard for an assessment of the achieved jitter compensation, use of very intense soft x-ray pulses from FLASH yields evidence of a decay channel not previously observed. With an ultrafast dynamical process as a reference, a direct comparison between the laser/x-ray cross-correlation and the EOS technique is possible, thereby contributing to the question as to whether a measurement of the electron timing can substitute for an all-optical cross-correlation
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