Atto-second time-delay in single and double photoionization of noble gas atoms

We perform a systematic investigation of the photoelectron group delay in valence shell single ionization of Ne, Ar, Kr and Xe from their respective thresholds to photon energy of 200 eV. This allows us to highlight various important aspects of fundamental atomic physics that can be probed by attosecond time delay measurements and to address several controversies in recent experiments. We also use these data as an input to the time delay calculations of single-photon double ionization (PDI) of noble gas atoms. Various PDI channels are examined and estimates are given for associated time delays due to the shake-off and knock-out processes. These estimates are used to interpret recent measurements of PDI of Xe on the atto-second time scale