Slow electrons from clusters in strong x-ray pulses

Electrons released from clusters through strong x-ray pulses show broad kinetic-energy spectra, extending from the atomic excess energy down to the threshold, where usually a strong peak appears. These low-energy electrons are normally attributed to evaporation from the nano-plasma formed in the highly-charged clusters. Here, it is shown that also directly emitted photo-electrons generate a pronounced spectral feature close to threshold. Furthermore, we give an analytical approximation for the direct photo-electron spectrum.