Abstract Details
Transition from Coulomb to Hydrodynamic Expansion of Rare Gas Clusters
Author: Benjamin Erk
Requested Type: Poster Only
Submitted: 2009-04-21 15:28:28
Co-authors: K. Hoffmann, B. Murphy, A. Helal, N. Kandadai, J. Keto, T. Ditmire
Contact Info:
Texas Center for High Intensity Laser Science
1 University Station, #C1510
Austin, Texas 78712
USA
Abstract Text:
The interaction of intense, ultrashort laser pulses with rare gas clusters is used as a model system to study the dynamics of complex systems by looking at the reaction products, i.e. electrons and ions. These clusters, held together by van der Waals forces, are produced in an expanding gas jet and consist of 100 to several 10000 atoms.
There are different mechanisms by which these clusters are ionized by an intense laser pulse, thus leading to divergent mechanisms of cluster expansion. For high intensities or small clusters a significant amount of the electrons is removed quickly and the cluster "Coulomb explodes" due to repulsive forces between the remaining positive ions. For lower intensities or larger clusters a smaller portion of the electrons is removed and some of them are confined inside the cluster and resonant heating is forming a nanoplasma. The expansion of these clusters is hydrodynamic.
We have studied the expansion dynamics of small and medium sized clusters of xenon and argon, driven by infrared light pulses at intermediate intensities. We analyzed the reaction products by taking time of flight measurements and determined the kinetic energy of ions and electrons.
By careful adjustment of laser intensity and cluster size we were, for the first time, able to measure intermediate behavior between hydrodynamic expansion and Coulomb explosion in a shell-like behavior.
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