The anomalous thermal radiation from metals produced by ultrashort laser pulses. I

The spectral-time characteristics of the secondary radiation induced in silver and tungsten by picosecond laser pulses of varying duration and fluence have been studied theoretically and experimentally. It is established that the secondary radiation is due to heating, but in silver, nevertheless, it is not usual and does not correspond, for example, to grey-body radiation. This radiation—the anomalous thermal radiation proceeds by the following mechanism: When the electron and phonon subsystems in a metal are heated (including also the nonisothermal process), there appears a glow with a continuous spectral distribution and an intensity exceeding the radiation intensity of the grey body whose temperature is equal to the temperature of the ion or electron subsystem of a metal. This anomaly is either due to overheating of the electron subsystem with respect to the ion subsystem or due to recombination of electrons and thermions in a microlayer above the metal surface.