Frankfurt 2006 – scientific programme

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SYIF: Intense field interaction with molecules and clusters

SYIF 2: Intense field interaction with molecules and clusters 2

SYIF 2.3: Invited Talk

Friday, March 17, 2006, 17:30–18:00, HV

Strong dual-pulse excitations of metal clusters — •Karl-Heinz Meiwes-Broer, Tilo Doeppner, Thomas Fennel, Johannes Passig, and Josef Tiggesbaeumker — Institute of Physics, University of Rostock, Universitaetsplatz 3, 18051 Rostock

Atomic clusters in intense laser fields are a nice playground to study the coupling of strong radiation into matter. In particular, non-stationary plasma effects lead to pronounced dynamics in the optical response. Recent experiments have shown that excitation with optically delayed dual pulses provides a powerful way to control the coupling of the radiation to these finite systems. Both the yield of highly charged atomic ions [1] as well as the kinetic energy of emitted electrons [2] are strongly enhanced for a particular optimal delay. After the first pulse initiates the cluster expansion the delay-dependent impact of the second pulse can be studied. In this contribution we will present experimental results on the charging dynamics by use of the femtosecond dual-pulse technique. Special emphasis will be put onto the role of the laser focus. The significance of the temporal structure of the laser field is demonstrated by complementary Vlasov calculations [3] on model systems. We attribute the distinct maximum in the charging efficiency to plasmon-enhanced ionization of the expanding cluster which is supported by the simulations [1]. Applying this method to free clusters and those which are embedded in helium droplets [4] reveals a significant influence of charge transfer processes which will be discussed.

[1] T. Doeppner, Th. Fennel, Th. Diederich et al., Phys. Rev. Lett. 94:013401, 2005

[2] T. Doeppner, Th. Fennel, P. Radcliffe et al., submitted

[3] Th. Fennel, G. Bertsch and K.H. Meiwes-Broer, Eur. Phys. J. D 29:367, 2004

[4] T. Doeppner, S. Teuber, Th. Diederich et al., Eur. Phys. J. D 24:157, 2003