Probing Single-Photon Ionization on the Attosecond Time Scale

Abstract

We study photoionization of argon atoms excited by attosecond pulses using an interferometric measurement technique. We measure the difference in time delays between electrons emitted from the 3s(2) and from the 3p(6) shell, at different excitation energies ranging from 32 to 42 eV. The determination of photoemission time delays requires taking into account the measurement process, involving the interaction with a probing infrared field. This contribution can be estimated using a universal formula and is found to account for a substantial fraction of the measured delay.

Distinguishing attosecond electron–electron scattering and screening in transition metals

“…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).…”

“…The RABBITT method (28)(29)(30) (reconstruction of attosecond beating by interference of twophoton transitions) has also been very successfully applied to atomic and material samples, where quantum interferences between neighboring two-photon transition pathways can modulate these sidebands as a function of the relative time delay between the HHG pump and IR probe pulses: Any time delay in photoemission from different initial or final states will lead to a phase delay in the interferograms (28,31).…”

Photoelectron spectrometer for attosecond spectroscopy of liquids and gases

“…Integrating the sideband intensity along the energy axis and fitting a sine curve to the sideband oscillation allows extracting the relative phases of the oscillations. Those are composed of three contributions, the XUV spectral phases for each harmonic, the Wigner delay and the measurement-induced continuum phase, the latter two often being referred to as the atomic phase 37,38 .…”

Double ionization probed on the attosecond timescale

“…After a decade where attosecond light sources 4,5 were characterized and their potential demonstrated, the next phase will include the exploration of correlated electron dynamics in complex systems. A series of ground-breaking studies on single ionization (SI) in atoms using attosecond light pulses sheds light on the escaping electron and its interaction with the residual ion 6,8 , and the resulting coherent superposition of neutral bound states 9,10 . Double ionization (DI) by absorption of a single photon is an inherently more challenging phenomenon, both experimentally and theoretically 1-3 .…”

“…A quantum mechanical description of SI time delays involved in attosecond interferometric experiments 6 (or similarly in streaking 8,23 ) shows that the measured delay is the sum of two different contributions: the group delay of the electronic wave packet created by one-photon absorption (τ 1ph SI ), which contains information on the atomic potential, and the delay added by the interaction with the infrared field [24][25][26] (τ cc ). In general τ 1ph SI = ∂ arg M/∂E, where M is the (complex) photoionization matrix element and E is the (total) kinetic energy (atomic units are used throughout).…”