High current and directional electron beams produced from gold photocathodes by ultrashort excimer laser pulses

Abstract
The surface photoelectric effect induced by 500 fs excimer laser pulses in a gold metallic target has been studied. Unexpectedly high current densities of 4 kA/cm2, induced by laser intensities in the 3 GW/cm2 range have been measured. Intense photoelectron emission could also be observed at laser intensities up to 10 GW/cm2 without plasma formation. Furthermore, an electron angular distribution of 18°±2° was obtained for laser intensities in the range of 1–3 GW/cm2. These results are compared to those obtained in previous work for single-photon and multiphoton photoeffects by using longer laser pulses, and their potential exploitation for free-electron laser and accelerator applications is discussed.