Steering Attosecond Electron Wave Packets with Light

Abstract

Photoelectrons excited by extreme ultraviolet or x-ray photons in the presence of a strong laser field generally suffer a spread of their energies due to the absorption and emission of laser photons. We demonstrate that if the emitted electron wave packet is temporally confined to a small fraction of the oscillation period of the interacting light wave, its energy spectrum can be up- or downshifted by many times the laser photon energy without substantial broadening. The light wave can accelerate or decelerate the electron's drift velocity, i.e., steer the electron wave packet like a classical particle. This capability strictly relies on a sub-femtosecond duration of the ionizing x-ray pulse and on its timing to the phase of the light wave with a similar accuracy, offering a simple and potentially single-shot diagnostic tool for attosecond pump-probe spectroscopy.

Attosecond electron wave packet interferometry

“…potential of the IR field, polarized in the same direction (y) as the XUV field, τ is the instant of ionization and e is the electron charge. This effect, which strongly depends on the initial timing 11,12 , has previously been used in attosecond metrology to determine the characteristics of single attosecond pulses 13 as well as of the IR laser field 14 .…”

Tunneling ionization of the F4 and D6 states of vanadium: Exchange blockade

“…For the quartet, the electrons in these orbitals have opposite spin, and there is no exchange interaction. Both ∆v (1) α of the sextet and ∆v (1) β of the quartet peak at r = 2.6 a 0 where they are about 2 eV. This elevates the ionization barrier and reduces the tunneling ionization rate for both states.…”

“…(18) is negative, which means that ∆v (0) β is attractive, particularly near the core. Following the electric field of the laser, ∆ρ (1) α peaks at a somewhat larger radial distance, which creates a repulsive potential that serves as an additional barrier for tunneling ionization. As such, dynamics of the second electron creates a ∆v (0) β that binds the electron more to the core and a ∆v (1) β that increases the tunneling barrier.…”

“…7 we compare the induced KS potentials ∆v (0) β of the quartet with ∆v (0) α of the sextet and ∆v (1) β of the quartet with ∆v (1) α of the sextet at the maximum field strength of I = 1.54 × 10 13 W/cm 2 at t m = T /2 + 3π/2ω. This peak intensity is chosen because the TDDFT calculated ionization probability of the quartet agrees well with the experimental data.…”

“…The emerging field of attosecond science [1,2] is based on the interaction of atoms and molecules with intense lasers. Currently, strong field theories often use the single active electron (SAE) approximation.…”