Electron emission from metal surfaces exposed to ultrashort laser pulses

The emission current and the charge emitted from a metal surface exposed to a picosecond laser pulse are determined. The competition between photoelectric and thermionic emissions is considered. It is shown that for intensities in excess of a critical value the emission current is entirely due to thermionic emission. At the same time, the emission pulse is practically undelayed relative to the laser pulse. This is due to the small specific heat of the degenerate electron gas which is practically thermally insulated from the lattice during the duration of the ultrashort laser pulse. It is noted that the electron-lattice relaxation kinetics can be investigated by measuring thermionic emission produced by ultrashort laser pulses.