Attosecond chronoscopy of photoemission

Abstract

Recent advances in the generation of well characterized sub-femtosecond laser pulses have opened up unpredicted opportunities for the real-time observation of ultrafast electronic dynamics in matter. Such attosecond chronoscopy allows a novel look at a wide range of fundamental photophysical and photochemical processes in the time domain, including Auger and autoionization processes, photoemission from atoms, molecules, and surfaces, complementing conventional energy-domain spectroscopy. Attosecond chronoscopy raises fundamental conceptual and theoretical questions as which novel information becomes accessible and which dynamical processes can be controlled and steered. These questions are currently a matter of lively debate which we address in this review. We will focus on one prototypical case, the chronoscopy of the photoelectric effect by attosecond streaking. Is photoionization instantaneous or is there a finite response time of the electronic wavefunction to the photoabsorption event? Answers to this question turn out to be far more complex and multi-faceted than initially thought. They touch upon fundamental issues of time and time delay as observables in quantum theory. We review recent progress of our understanding of time-resolved photoemission from atoms, molecules, and solids. We will highlight the unresolved and open questions and we point to future directions aiming at the observation and control of electronic motion in more complex nanoscale structures and in condensed matter.

Distinguishing attosecond electron–electron scattering and screening in transition metals

“…To date, two approaches have been used to probe attosecond electron dynamics in matter through photoemission, taking advantage of laser-assisted photoemission sidebands (24,25). For atoms, because the energy separation between different states is large, attosecond streaking using isolated attosecond pulses (with an energy resolution of several electronvolts) has been applied very successfully (26,27). The same approach has also been used to measure the transit time for a photoelectron to be emitted Significance Electron-electron interactions are among the fastest processes in materials that determine their fascinating properties, occurring on attosecond timescales on up (1 as = 10 −18 s).…”

“…High harmonic generation (HHG) provides attosecond pulses and pulse trains that are perfectly synchronized to the driving laser and that are ideal for probing the fastest coupled charge and spin dynamics in atoms, molecules, and materials (23)(24)(25)(26)(27)(28)(29)(30)(31)(32)(33). To date, two approaches have been used to probe attosecond electron dynamics in matter through photoemission, taking advantage of laser-assisted photoemission sidebands (24,25).…”

Phase-retrieval algorithm for the characterization of broadband single attosecond pulses

“…Such inaccuracy in the FROG-CRAB method would induce error of the retrieved atomic dipole phase, as well as the retrieved "photoionization time delay", which has been widely investigated in recent years on different targets. Unprecedented "accuracy" of the extracted "time delay" has often been quoted in these studies without accounting for the intrinsic error of the retrieval method [30].…”

Time-resolved electron(e,2e)momentum spectroscopy: Application to laser-driven electron population transfer in atoms

“…Studies of time-resolved electron dynamics in various atomic, molecular, and condensed-matter reactions have increased over the past two decades [1][2][3][4][5][6][7] owing to experimental progress in generating ultrashort and/or intense pulses of extreme ultraviolet light [8,9], x rays [10,11], and electrons [12,13]. These advances open the possibility of obtaining a deeper understanding of physical and chemical reaction mechanisms.…”