On the analysis of photo-electron spectra

TL;DR

This paper develops a generalized framework for analyzing photo-electron spectra (PES) across various excitation mechanisms, including complex multi-frequency pulses, by linking spectral distributions of multipole moments to PES features.

Contribution

It introduces an extended rule for interpreting PES that accounts for mixed frequencies and resonant excitations, applicable to attosecond experiments.

Findings

Spectral distributions of multipole moments correlate with PES features.

The generalized relation explains photo-electron yields in complex excitation scenarios.

The approach covers simple to complex excitation mechanisms.

Abstract

We analyze Photo-Electron Spectra (PES) for a variety of excitation mechanisms from a simple mono-frequency laser pulse to involved combination of pulses as used, e.g., in attosecond experiments. In the case of simple pulses, the peaks in PES re- flect the occupied single-particle levels in combination with the given laser frequency. This usual, simple rule may badly fail in the case of excitation pulses with mixed frequencies and if resonant modes of the system are significantly excited. We thus develop an extension of the usual rule to cover all possible excitation scenarios, including mixed frequencies in the attosecond regime. We find that the spectral dis- tributions of dipole, monopole and quadrupole power for the given excitation taken together and properly shifted by the single-particle energies provide a pertinent picture of the PES in all situations. This leads to the derivation of a generalized relation allowing to understand photo-electron yields even in complex experimental setups.