Attosecond Control of Ionization Dynamics

TL;DR

This paper demonstrates control over helium ionization using synchronized attosecond pulse trains and IR fields, revealing wave packet interference effects in a strongly driven atomic system.

Contribution

It introduces a novel method to manipulate and observe wave packet interference in atoms using attosecond pulse trains synchronized with IR fields.

Findings

Ionization probability depends on delay between IR and attosecond pulses

Interference between bound electron wave packets controls ionization

First observation of wave packet interference in a strongly driven atom

Abstract

Attosecond pulses can be used to initiate and control electron dynamics on a sub-femtosecond time scale. The first step in this process occurs when an atom absorbs an ultraviolet photon leading to the formation of an attosecond electron wave packet (EWP). Until now, attosecond pulses have been used to create free EWPs in the continuum, where they quickly disperse. In this paper we use a train of attosecond pulses, synchronized to an infrared (IR) laser field, to create a series of EWPs that are below the ionization threshold in helium. We show that the ionization probability then becomes a function of the delay between the IR and attosecond fields. Calculations that reproduce the experimental results demonstrate that this ionization control results from interference between transiently bound EWPs created by different pulses in the train. In this way, we are able to observe, for the first time, wave packet interference in a strongly driven atomic system.