We investigate the resonance-enhanced few-photon ionization of atomic lithium by linearly polarized light whose frequency is tuned near the $2s\text{−}2p$ transition. Considering the direction of light polarization orthogonal to the quantization axis, the process can be viewed as an atomic “double-slit experiment” where the $2p$ states with magnetic quantum numbers $m_{\ell }=\pm 1$ act as the slits. In our experiment, we can virtually close one of the two slits by preparing lithium in one of the two circularly polarized $2p$ states before subjecting it to the ionizing radiation. This allows us to extract the interference term between the two pathways and obtain complex phase information on the final state. The experimental results show very good agreement with numerical solutions of the time-dependent Schrödinger equation. The validity of the two-slit model is also analyzed theoretically using a time-dependent perturbative approach.

• Received 27 April 2022
• Revised 28 June 2022
• Accepted 18 July 2022

DOI:https://doi.org/10.1103/PhysRevA.106.023113