Stuttgart 2012 – scientific programme
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A: Fachverband Atomphysik
A 31: Interaction with strong or short laser pulses IV
A 31.3: Talk
Thursday, March 15, 2012, 11:15–11:30, V57.05
Time-resolved Dynamics after fs-excitation of Magnesium embedded in Helium Nanodroplets — •Sebastian Göde, Robert Irsig, Josef Tiggesbäumker, and Karl-Heinz Meiwes-Broer — Institut für Physik, Universität Rostock, Universitätsplatz 3, 18051 Rostock, D
Magnesium atoms embedded in droplets show an interesting spectroscopic pattern when excited with ns laser pulses. An absorption feature near the atomic 3 1P10 ← 3 1S0 transition is obtained, irrespective on the doping level. This observation is consistent with the assumption of a metastable foam like structure, where the helium prevents a relaxation into the structural ground state [1].
In the present study we conducted off-resonance fs pump-probe experiments to analyze the real time dynamics. By varying the pulse energy and ratio of the subpulses, different excitation regimes have been investigated. At low intensities 1012W/cm2, the cluster ion signals show a notable dependence on the order when unbalanced pulses are used. A weaker prepulse favors the appearance of cluster ions, while fragments are enhanced when stronger prepulses are used. When increasing the laser intensity a clear pump-probe signature evolves. Possible ionisation scenarios for compact clusters and a foam like constitution are discussed.
[1] A. Przystawik, S. Göde et. al., PRA 78, 021202 (2008)