Hannover 2016 – wissenschaftliches Programm

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A: Fachverband Atomphysik

A 15: Atomic clusters II (with MO)

A 15.6: Vortrag

Dienstag, 1. März 2016, 15:45–16:00, f107

Slow electrons from direct photoionization in clusters — •Abraham Camacho Garibay, Ulf Saalmann, and Jan-Michael Rost — MPI-PKS, Dresden

Sequential ionization of clusters by intense XFEL pulses is known to give a broad plateau like photoelectron spectrum. For sufficiently high charge states, the coulomb potential can be deep enough to trap the outgoing photoelectron, giving rise to a nanoplasma (an effect known as frustrated ionization). This nanoplasma eventually thermalizes and evaporates, giving rise to a high peak near zero. We have found that this high peak is formed not only by evaporating plasma electrons, but it also has a component from directly emitted photoelectrons that naturally arises during the transition between the sequential ionization regime into the frustrated ionization one. We have found that this effect can be explained in a simple way by noting that plasma electrons do not increase the system charge, which requires a small modification in the probability of electron emission as a function of position. By making a simple approximation it is possible to obtain an analytical formula with good agreement with the results obtained by means of molecular dynamics simulations.