Multi-plasmon excitations in electron spectra of small systems irradiated by swift charged projectiles

TL;DR

This study explores how resonant modes influence the electron emission spectra of small systems excited by swift charged particles, revealing that resonances can produce distinct peaks similar to laser-induced spectra.

Contribution

It demonstrates that resonance modes significantly affect photo-electron spectra in small systems excited by swift ion collisions, expanding understanding beyond photon-driven processes.

Findings

Resonance modes create distinct peaks in electron spectra.

Patterns similar to laser-induced spectra are observed.

Resonances are a new source of spectral peaks.

Abstract

We investigate the kinetic-energy spectrum of electrons emitted from an excited many-electron system, often called photo-electron spectrum (PES). We are particularly interested on the impact of resonant modes of the system on PES. To this end, we consider three systems with strong resonances, a Mg atom, the small alkaline cluster ${{\rm K}_9}^+$, and the small carbon chain C$_3$. To avoid dominant frequencies in the excitation process, we consider a collision with a fast ion which is realized by an instantaneous boost of the valence electrons, a process which excites all frequencies with equal weight. The electron dynamics is investigated from a theoretical perspective using time-dependent density-functional theory augmented by an average-density self-interaction correction. We observe patterns which are similar to PES usually obtained after irradiation by a laser pulse, in particular the appearance of clear peaks. We show that these patterns are driven by strong resonance modes of the system. Resonances are thus found to be another source of peaks in the PES, besides photons (when present) with definite frequencies.