On the dynamics of photo-electrons from C$_{60}$

TL;DR

This paper uses real-time TDDFT to analyze photo-electron spectra and angular distributions of C60, revealing how ionization processes depend on photon energy and laser intensity, with implications for understanding molecular ionization dynamics.

Contribution

It applies time-dependent density functional theory to study photo-electron emissions from C60, including orientation averaging and multi-photon ionization, providing detailed insights into ionization mechanisms.

Findings

PES map energies and depletion of single-particle states.

PES show regular peaks separated by photon energy in multi-photon ionization.

PAD anisotropy increases with photon order.

Abstract

We explore photo-electron spectra (PES) and photo-electron angular distributions (PAD) of C$_{60}$ with time-dependent density functional theory (TDDFT) in real time. To simulate experiments in gas phase, we consider isotropic ensembles of cluster orientations and perform orientation averaging of the TDDFT calculations. First, we investigate ionization properties of C$_{60}$ by one-photon processes in the range of VUV energies. The PES map the energies of the occupied single-particle states, while the weights of the peaks in PES are given by the depletion of the corresponding level. The different influences can be disentangled by looking at PES from slightly different photon frequencies. PAD in the one-photon regime can be characterized by one parameter, the anisotropy. This single parameter unfolds worthwhile information when investigating the frequency and state dependences. We also discuss the case of multi-photon ionization induced by strong infrared laser pulses in C$_{60}$. In agreement with measurements, we find that the PES show a regular comb of peaks separated by the photon energy. Our calculations reveal that this happens because only very few occupied states of C$_{60}$ near the ionization threshold contribute to emission and that these few states happen to cooperate filling the same peaks. The PAD show a steady increase of anisotropy with increasing photon order.