Electron and Ion Emission from Clusters exposed to Strong Laser Fields

When clusters interact with intense optical laser pulses energetic and highly charged atomic fragment ions e.g. are generated$^1$. In contrast to atoms the efficiency of the process could be enhanced by choosing a pair of optical delayed pulses instead of a single but more intense femtosecond pulse$^2$. In metals the stronger charging of the clusters can qualitatively be explained by a plasmon enhanced ionization process. We extended our studies and have made a compared analysis of the emission of highly charged ions and energetic electrons the interaction dynamics of intense femtosecond laser fields with nanometer-sized silver clusters. Using a pair of laser pulses with variable optical delay the time-dependent cluster response is resolved. A dramatic increase both in the atomic charge state of the ions and the maximum electron kinetic energy is observed for a certain delay of the pulses. Corresponding Vlasov calculations on a metal cluster model system indicate that enhanced cluster ionization as well as the generation of fast electrons coincide with resonant plasmon excitation.$^3$ \begin{enumerate} \item L.~K{\"o}ller, M.~Schumacher, J.~K{\"o}hn, S.~Teuber, J.~Tiggesb{\"a}umker, and K.-H. Meiwes-Broer, Phys. Rev. Lett. {\bf 82}, 3783 (1999). \item T.~D{\"o}ppner, Th. Fennel, Th. Diederich, J.~Tiggesb {\"a}umker, and K.-H. Meiwes-Broer, Phys. Rev. Lett. {\bf 94}, 013401 (2005). \item Th.~Fennel, G.F. Bertsch, and K.-H. Meiwes-Broer, Eur. Phys. J. D {\bf 29}, 367 (2004). \end{enumerate}