Effect of the finite speed of light in ionization of extended systems

TL;DR

This paper develops a quantitative theory for how the finite speed of light influences ionization in extended systems, showing that these effects can be observed in photoelectron distributions and measured with tabletop lasers.

Contribution

It introduces a general theory of finite light speed effects in ionization, highlighting their manifestation in non-dipole terms and providing a practical method for experimental detection.

Findings

Finite light speed effects appear in photoelectron momentum distributions.

Numerical modeling confirms measurable propagation delays in molecular ionization.

Tabletop laser experiments can determine light propagation times more easily than synchrotron methods.

Abstract

We study propagation effects due to the finite speed of light in ionization of extended systems. We present a general quantitative theory of these effects and show under which conditions such effects should appear. The finite speed of light propagation effects are encoded in the non-dipole terms of the time-dependent Shr\"odinger equation and display themselves in the photoelectron momentum distribution projected on the molecular axis. Our numerical modeling for the \Hp molecular ion and the \Ne dimer shows that the finite light propagation time from one atomic center to another can be accurately determined in a table top laser experiment which is much more readily affordable than an earlier synchrotron measurement by Grundmann {\em et al} [Science 370, 339 (2020)]