Abstract
Recent progress in the generation of ultra-short laser pulses has enabled the measurement of photoionization time delays with attosecond precision. For single photoemission time delays the most common techniques are based on attosecond streaking and the reconstruction of attosecond beating by interference of two-photon transitions (RABBITT). These are pump-probe techniques employing an extreme-ultraviolet (XUV) single attosecond pump pulse for streaking or an attosecond pump pulse train for RABBITT, and a phase-locked infrared (IR) probe pulse. These techniques can only extract relative timing information between electrons originating from different initial states within the same atom or different atoms. Here we address the question whether the two techniques give identical timing information. We present a complete study, supported by both experiments and simulations, comparing these two techniques for the measurement of the photoemission time delay difference between valence electrons emitted from the Ne 2p and Ar 3p ground states. We highlight not only the differences and similarities between the two techniques, but also critically investigate the reliability of the methods used to extract the timing information.
Highlights
The possibility to investigate attosecond ionization time delays in atoms was demonstrated almost one decade ago with the first experiments in the strong field regime [1,2], where an atom was ionized with a photon energy much lower than the ionization potential
Our experiments are performed with a so-called AttoCOLTRIMS apparatus, which consists of a reaction microscope or Cold Target Recoil Ion Momentum Spectroscopy (COLTRIMS) allowing for full 3D-coincidence detection [21] combined with an attosecond front-end, providing single attosecond pulse (SAP) and attosecond pulse train (APT) with photon energies in the XUV spectral range [22]
The APT or SAP provides the XUV pump pulse and is focused into the gas jet target that contains a mixture of argon and neon in equal amounts in order to simultaneously ionize both species under identical experimental conditions
Summary
The possibility to investigate attosecond ionization time delays in atoms was demonstrated almost one decade ago with the first experiments in the strong field regime [1,2], where an atom was ionized with a photon energy much lower than the ionization potential. The most common techniques to investigate the single-photon photoemission time delay are based on either the attosecond energy streaking [9,10] or the reconstruction of attosecond beating by interference of two-photon transitions (RABBITT) [11,12]. Both techniques employ a pump-probe scheme, where an extreme-ultraviolet (XUV) pump pulse initiates electron dynamics and an infrared (IR) probe pulse interrogates the temporal evolution as the delay between pump and probe is varied. While the RABBITT technique uses an attosecond pulse train (APT) in combination with a less intense and typically longer IR pulse, attosecond streaking method uses a single attosecond pulse (SAP) as a pump and a more intense, few-cycle IR pulse as a probe
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