Attosecond streaking of shake-up and Auger electrons in xenon

Abstract

Abstract. We present first results of simultaneous attosecond streaking measurements of shake-up electrons and Auger electrons emitted from xenon. We extract relative photo-emission delays for electrons emitted from the 4d, 5s and 5p subshell, as well as for the 5p -2 5d correlation satellite (shake-up electrons).The recent advances in attosecond physics revealing an emission delay between electrons emitted from valence states and deeper bound 4f states in tungsten [1] and from the 2p and 2s subshells in neon [2] have provoked and will continue to provoke questions about the physics of photoionization. However, in the aforementioned experiments a relative phase ambiguity remained, because of the spectral separation of the respective emitted wavepackets. We present experimental data obtained using this method from an atomic system, xenon, from which more different electron wavepackets including shake-up electron wavepackets are emitted, and where a spectral overlap of some of these wavepackets can be observed. The spectral overlap of the different emitted electronic wavepackets can eliminate the relative phase ambiguity, and thus allows for a more reliable measurement of the relative emission phase and delay. Recently, attosecond spectroscopic measurements from xenon using a velocity map imaging (VMI) spectrometer were reported [3], revealing a weak phase sensitivity of sideband generation of the Auger emission, in agreement with numerical simulations presented previously [4]. Although VMI has the advantage that the angular distribution of the electrons can be obtained, the spectral resolution was much lower than that of our linear time-of-flight spectrometer [5], such that the individual Auger lines could not be resolved and no information about the valence electrons was obtained. In the experimental data we present here, the Auger lines and corresponding sidebands are individually resolved, and the streaking of the 5p, 5s and 4d photoelectrons and the 5p -2 5d shake-up satellite is well resolved.Carrier envelope phase (CEP) stable 5-fs pulses with a central wavelength of ~750 nm and ~250 µJ energy are generated by focusing 700 µJ, 25 fs pulses from a CEP stabilized Ti:sapphire multipass amplifier in a neon-filled capillary and subsequent compression in a chirped mirror compressor. Through loose focusing of the CEP stable few-cycle pulses on a neon target, highharmonics are generated. The few-cycle pulses are spatially separated from the generated harmonics using an annular filter consisting of a pellicle with a central hole that is covered with a Zr foil. This is an Open Access article distributed under the terms of the Creative Commons Attribution License 2.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.