Emission of Thermally Activated Electrons from Rare Gas Clusters Irradiated with Intense VUV Light Pulses from a Free Electron Laser

Laarmann T, Rusek M, Wabnitz H, Schulz J, de Castro AR, Gürtler P, Laasch W, Möller T

The ionization dynamics of Ar and Xe clusters irradiated with intense vacuum ultraviolet light from a free-electron laser is investigated using photoelectron spectroscopy. Clusters comprising between 70 and 900 atoms were irradiated with femtosecond pulses at 95 nm wavelength (~13 eV photon energy) and a peak intensity of ~4×1012 W/cm2. A broad thermal distribution of emitted electrons from clusters with a maximum kinetic energy up to 30–40 eV is observed. The observation of relatively low-energy photoelectrons is in good agreement with calculations using a time-dependent Thomas-Fermi model and gives experimental evidence of an outer ionization process of the clusters, due to delayed thermoelectronic emission.

Phys Rev Lett. 2005 Aug 5;95(6):063402. Epub 2005 Aug 5