Fig. 1: Schematic representation of the core-hole-clock method.

a In the first step, below the metal-cation ionization threshold, a core electron is excited to the virtual orbitals and leaves a hole in the coreshell. If the excited electron remains localized in the atomic orbital, a spectator Auger–Meitner (AM) electron is emitted (upper process, yielding the red peak in panel b). If the electron delocalizes into the environment, a normal AM electron is emitted (lower process, yielding the blue peak in panel b). b Depending on the core-hole lifetime, τ1s, and the delocalization time, τdelocalization, different spectator and normal AM electron signal-intensity ratios are obtained.