Phase, time and correlations in free electron wave packets

Introduction

Electron emission from matter is a widespread phenomenon in nature, with examples including the photoionization of atoms and molecules, photoemission from solids, and the release of electrons due to ionizing radiation in biology. Complete information about the emitted electrons is contained in the amplitude and phase of their wave packets.

Research Goals

While state-of-the-art electron spectroscopy routinely accesses the amplitude of these wave packets, the phase of free electron wave packets remains inaccessible. My team and I aim to develop an experimental technique to measure the phase of free electron wave packets without interfering with their creation mechanism. This will be groundbreaking, as the phase of the free electron wave packet carries information about the quantum mechanical properties of photoionization and the electron in its bound state prior to ionization.

Methodology

We will accomplish this task by constructing a novel, microscopic, ultrafast free-electron interferometer, in which replicas of the initial free electron wave packet are generated, shifted in momentum space, and brought to interference. At the heart of this innovative interferometric scheme are two crossed pulsed standing light waves that interact with the wave packet after its creation on femtosecond timescales.

We will scale this approach to be applicable to correlated few-body wave packets by combining the light field interferometer with coincident multi-particle detection in a COLTRIMS reaction microscope.

Objectives

Employing this groundbreaking method, we will address three objectives:

1. We will investigate the time evolution of the phase of an atomic photoelectron wave packet with a linear and with a helical interferometer made from light carrying orbital angular momentum.
2. We will study wave packets emitted from molecules, including chiral molecules.
3. We will examine correlations and entanglement within two-electron wave packets and between photoelectrons and their parent ions.