Separation of photoionization and measurement-induced delays

Abstract

Photoionization of matter is one of the fastest electronic processes in nature. Experimental measurements of photoionization dynamics have become possible through attosecond metrology. However, all experiments reported to date contain a so-far unavoidable measurement-induced contribution, known as continuum-continuum (CC) or Coulomb-laser-coupling delay. In traditional attosecond metrology, this contribution is nonadditive for most systems and nontrivial to calculate. Here, we introduce the concept of mirror symmetry–broken attosecond interferometry, which enables the direct and separate measurement of both the native one-photon ionization delays and the CC delays. Our technique solves the longstanding challenge of experimentally isolating these two contributions. This advance opens the door to the next generation of accurate measurements and precision tests that will set standards for benchmarking the accuracy of electronic structure and electron-dynamics methods.

Understanding attosecond streaking

“…A free electron (i.e. without Coulomb and without laser) that moves at speed v ∞ travels the same distance in a different time span δt free : δr = v ∞ δt free (57) and thus we can write…”

“…Those very same issues are also relevant in the interpretation of delays obtained in Reconstruction of Attosecond Beating By Interference of Two-photon transitions (RABBIT) [52,55,56], a technique based on interferometry that also aims at measuring ionization delays by applying an XUV and IR pulse. RABBIT has also been widely applied to atoms, molecules, liquids and solids [57][58][59][60][61][62][63][64][65][66][67][68][69][70][71][72] and has been shown to give results that are equivalent to those obtained by attosecond streaking [9,61,73,74]. In RABBIT experiments the CLC is often referred to as continuum-continuum coupling (usually abbreviated as CC) but describes the same effect [9,39,65,73].…”

“…Normally, experimental measurements can only measure the total delay and are therefore not able to separate out the CLC or CC coupling from the Wigner delays in streaking and RABBIT experiments, respectively. However, a recent experiment [57] used the concept of mirror symmetry-broken attosecond interferometry to isolate the CC delay. This experiment found that the experimentally measured CC delay compares well with theoretical predictions (see figure 4 of [57]).…”

“…However, a recent experiment [57] used the concept of mirror symmetry-broken attosecond interferometry to isolate the CC delay. This experiment found that the experimentally measured CC delay compares well with theoretical predictions (see figure 4 of [57]). This provides experimental confirmation to the theory that we discuss here, due to the correspondence between CLC and CC delays [73].…”