Attosecond Streaking Time Delays: Finite-Range Interpretation and Applications

Abstract

We review theoretical studies of the attosecond streaking time delay concept in photoionization via the investigation of the electron dynamics in the streaking field after the transition of the photoelectron into the continuum upon absorption of an extreme ultraviolet photon. Based on the results, a so-called finite range interpretation was introduced, which highlighted that the delay is accumulated until the streaking pulse ends and, hence, over a finite range of the potential of the parent ion. Following a discussion of the analysis leading to this interpretation, we summarize a few applications which provide insights into different aspects of the streaking time delay concept in photoionization. Besides a review of previously presented results, we give an analysis of the relevance of the first half-cycle of the streaking field and an outlook regarding the perspective of using the streaking method to resolve dynamical changes in the potential that the photoelectron explores during its propagation in the continuum.

Understanding attosecond streaking

“…It not only leads to a strong dependence of the delay on the soft-core parameter SC that necessarily has to be included in such a one-dimensional system (−Z/x → −Z/ √ x 2 + SC), but it also lacks the centrifugal barrier term l 2 /(2r 2 ). Nonetheless, many studies of the delay in the Coulomb potential do so in a one-dimensional Coulomb potential 1/r without centrifugal term [13,32,36,[45][46][47][48]51], which leads to confusion as the results can (most of the time) not be compared directly to results of the actual 3D situation.…”

“…Despite those problems, we can find several studies that use a 1D model to describe delays in a 3D Coulomb potential [13,32,36,[45][46][47][48]51]. In some cases this may be appropriate, such as when demonstrating the connection between the original definition of the Wigner delay as due to scattering and the photoionization delay [41].…”

“…Thus, the 'actual' ionization delay t EWS is usually obtained by subtracting the term t CLC from the value t s that one extracts directly from the measurement. How to calculate the CLC term and how the CLC time and the measured streaking delay t s relate to each has sparked many discussions [13,35,36,[43][44][45][46][47][48][49][50][51][52][53][54].…”

“…In section 3, we will then consider how using an IR field affects the measured ionization delay and how this result relates to the scattering delay obtained without an IR field. We will do this by deriving the total streaking delay and the CLC term in a way that allows to compare the seemingly disparate approaches and results one can currently only find scattered over several publications [13,35,36,44,46,51]. This will then also allow us to test under which conditions splitting of the streaking delay into an EWS and CLC term is physically meaningful.…”

Reconstruction of attosecond pulses in the presence of interfering dressing fields using a 100 kHz laser system at ELI-ALPS

“…Ever since the discovery of high-harmonic generation (HHG) [1], it has proven a valuable source of tabletop extreme-ultraviolet (XUV) radiation. As an added benefit over synchrotrons and X-ray free-electron lasers, HHG can produce laser pulses with attosecond temporal duration [2,3], making it a powerful tool for studying electronic dynamics on sub-femtosecond time scales [4][5][6][7][8][9][10][11][12][13][14][15][16][17]. If a many-cycle infrared (IR) pulse is used for HHG, a set of discrete XUV harmonics are produced, resulting in an attosecond pulse train (APT) [2,3].…”