| We will discuss the response of atomic clusters to intense femtosecond laser pulses. We start with the description of clusters in long wavelengths (near-infrared) fields where the optical cycle is longer than typical electron periods and ionization occurs via atomic field ionization. Cluster are very efficiently excited under certain conditions via collective dipole oscillations. We discuss implications of this process which have been observed also experimentally. In X-ray pulses the optical cycles are much shorter and thus predominantly inner-shell electrons are "kicked out". The created holes are filled by Auger decays. The influence of neighboring ions in a cluster on these processes are discussed. Furthermore we have studied the impact of static fields due to the strongly charged cluster which will considerably alter the explosion dynamics of the cluster. It is mainly this explosion dynamics which has to be understood in order to allow for coherent diffractive imaging in upcoming X-ray free-electron-laser machines. |
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