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A: Fachverband Atomphysik

A 8: Poster I

A 8.1: Poster

Dienstag, 9. März 2010, 16:30–19:00, Lichthof

General mechanisms of electron dynamics in FEL-irradiated clusters — •Christian Gnodtke, Ulf Saalmann, and Jan-Michael Rost — Max-Planck-Institut für Physik komplexer Systeme, Nöthnitzer Straße 38, 01187 Dresden

We describe the dynamics of electrons in clusters induced by radiation from free-electron lasers (FEL). Based on a simple molecular dynamics model with only four parameters, the total number of ionization events, the cluster radius, the atomic excess energy of the dominant ionization process and the pulse duration, we study the electron motion microscopically. The general dynamics may be categorized into four main parameter regions distinguished by the degree of electron trapping as well as the cross-over from sequential to non-sequential ionization. We identify within this parameter space the previously studied cases of a trapped equilibrium [1] and non-equilibrium plasma [2] as well as the regime of sequential ionization of the cluster [3]. Of particular interest is the region of non-sequential ionization with high excess energy for which we observe the novel phenomenon of ultra-fast formation of an exponential spectrum of the electrons, indicative of an equilibration of the electron system in the continuum.

[1] Ch. Bostedt et al. (experiment), U. Saalmann et al. (theory), to be published
[2] U. Saalmann et al., New J. Physics 10, 025014 (2008)
[3] Ch. Bostedt et al., Phys. Rev. Lett. 100, 133401 (2008)