Zero-energy photoelectric effect

TL;DR

This paper predicts a novel zero-energy peak in multi-photon ionization spectra, arising from the dominance of bound-continuum transitions, with specific conditions for experimental observation, especially in negative ions.

Contribution

It introduces the concept of a zero-energy photoelectric effect in multi-photon ionization, highlighting the conditions under which it occurs and its dependence on pulse duration and binding energy.

Findings

Zero-energy peak position depends on binding energy and pulse duration.

Bound-continuum transitions are stronger than continuum-continuum transitions.

Negative ions are ideal candidates for observing this effect.

Abstract

We predict a near-threshold ("zero energy") peak in multi-photon ionization for a dynamical regime where the photon frequency is large compared to the binding energy of the electron. The peak position does not depend on the laser frequency, but on the binding energy and the pulse duration. The effect originates from the fact that bound-continuum dipole transitions are stronger than continuum-continuum ones. To clearly observe this zero-energy photoelectric effect, the spectral width of the laser pulse should be comparable to the binding energy of the ionized orbital, and the second ionization potential should be larger than the photon energy. This suggests negative ions as ideal candidates for corresponding experiments.