Attosecond Ionization and Tunneling Delay Time Measurements in Helium

Abstract

It is well established that electrons can escape from atoms through tunneling under the influence of strong laser fields, but the timing of the process has been controversial and far too rapid to probe in detail. We used attosecond angular streaking to place an upper limit of 34 attoseconds and an intensity-averaged upper limit of 12 attoseconds on the tunneling delay time in strong field ionization of a helium atom. The ionization field derives from 5.5-femtosecond-long near-infrared laser pulses with peak intensities ranging from 2.3 x 10(14) to 3.5 x 10(14) watts per square centimeter (corresponding to a Keldysh parameter variation from 1.45 to 1.17, associated with the onset of efficient tunneling). The technique relies on establishing an absolute reference point in the laboratory frame by elliptical polarization of the laser pulse, from which field-induced momentum shifts of the emergent electron can be assigned to a temporal delay on the basis of the known oscillation of the field vector.

High-Harmonic Spectroscopy: From Femtosecond to Attosecond Molecular Dynamics

“…The last few years have seen first successes in the observation of electronic dynamics on this time scale. [3][4][5][6][7] These techniques will enable a new experimental access to electronic structure and electron correlation, which is one of the most challenging problems in chemistry and physics.…”

Attosecond tracing of correlated electron-emission in non-sequential double ionization

“…The identification of suitable approximations that capture the essential features of MED relies on the development of experiments aimed at resolving the electron dynamics on the characteristic attosecond timescale of their motion. An established technique for resolving one-electron dynamics on subfemtosecond scales involves the use of a strong few-cycle infrared laser field as a clock [1][2][3] . The well-known concept of attosecond streaking spectroscopy has permitted the observation of singleelectron dynamics with attosecond time resolution 4 .…”

Attosecond control of collective electron motion in plasmas

“…On the one hand, ultrahigh light intensities provided by multi-terawatt femtosecond lasers can be used to drive collective electron motion in plasmas up to the 0.1-1 gigaelectronvolt energy range [1], opening the way to very compact laser-based particle accelerators for nuclear and medical applications [2]. On the other hand, controlled few-cycle light waves can be used at moderate intensities to drive and probe the attosecond dynamics of few-electron motion in atoms [3,4,5,6], molecules [7,8] and condensed matter [9,10] -with typical energies * These authors contributed equally to this work. …”