An ultrashort light pulse illuminating a metal surface interacts primarily with the electrons. During a transient phase the electrons can be much hotter than the lattice. A two-temperature model predicts that the optical damage threshold of metals will be independent of the optical pulse duration for short pulses. Experiments performed with picosecond 10 um pulses confirm this prediction. The model also predicts, and we experimentally observe, electron emission during the transient phase even for illumination intensities below the damage threshold.
N. K. Sherman,
P. B. Corkum,
F. A. Hegmann,
"Transient Response Of Metals To Ultrashort Pulse Excitation," Optical Engineering 28(10), 281114 (1 October 1989). http://dx.doi.org/10.1117/12.7977096