Time-domain Measurement of Auger Electron Dynamics in Xenon and Krypton Atoms after Giant Resonance Photoionization

Time-resolved measurement of Auger-Meitner decay [Drescher et al., Nature (London) 419, 803 (2002)NATUAS0028-083610.1038/nature01143] marked a milestone in the development of attosecond science. To date, the time constants for the Auger-Meitner decay processes obtained from the time-domain experiments were found to be consistent with the values deduced from conventional energy-domain measurements. One of the main factors limiting the temporal resolution of these studies is the unlocked carrier-envelope-phase (CEP) of the laser pulses used to probe the electronic dynamics triggered by inner-shell photoabsorption. In this Letter, we report time-resolved inner-shell electron spectroscopy of xenon and krypton using attosecond soft x-ray (atto-SXR) pulses centered at 130 eV in combination with CEP-stabilized few-cycle Yb laser pulses. We observed that the N_{4,5}OO Auger electrons from xenon exhibit a clear streaking pattern, but with an unexpected time shift of ∼1.32  fs relative to the 4d photoelectrons. Furthermore, the energy-integrated yield of streaked Auger electrons from xenon exhibits a pronounced minimum at a pump-probe time delay of 4 fs. Neither of these observations can be explained by current streaking theories and both are inconsistent with lifetimes inferred from energy-domain measurements. The M_{4,5}NN Auger electrons from krypton partly overlap in energy with the 3d inner-shell photoelectrons and do not show these anomalous features. This Letter offers new insights into the inner-shell electron dynamics of heavy atoms in the giant dipole resonance region, laying the groundwork for attosecond soft x-ray spectroscopy of molecular systems containing iodine or bromine atoms.