Free-Electron Laser Ionizes Clusters

Investigations at Deutsches Elektronen Synchrotron in Hamburg, Germany, into the interaction of high-intensity, deep-UV radiation from a free-electron laser with clusters of xenon suggest that physicists will have to revisit their understanding of absorption processes. A report of the work appeared in the Dec. 5 issue of Nature.

The researchers exposed clusters of 1500 xenon atoms to 100-fs pulses of 98-nm radiation from the free-electron laser at power densities of up to 7 x 10¹³ W/cm². At the highest power densities, they found charge states up to Xe⁸⁺ (atomic Xe ions). Moreover, they detected Coulomb explosion at power densities as low as 10 W/cm², indicating that the clusters absorb more energy than predicted by current theory.