Attosecond dynamics of photoemission over a wide photon energy range

Abstract

Dynamics of photoemission from surfaces are usually studied at low photon energies (<100 eV). Here, we report on new findings on these dynamics observed at a tungsten surface on the attosecond time scale at photon energies exceeding 100 eV, over a range of almost 50 eV. While photoemission, a fundamental process in quantum mechanics, is often described within a semiclassical three-step model, we find that even at high photon energies only a full quantum treatment in one step predicts the measured attosecond dynamics correctly. On this time scale the intuitive, mechanistic interpretation of the photoelectric effect breaks down. This underlines the necessity to further develop experimental and theoretical tools to be used in improving our understanding of the fundamental process of light-matter interaction underlying many methods in extreme ultraviolet and soft x-ray spectroscopy.