Abstract:
The hypothesis is put forward on the basis of experimental data that strong inhomogeneous heating of the skin layer of conducting materials by a femtosecond pulse gives rise to a double electrical layer that is formed of a «surface» layer of positive ions and a thin (about $1$ nm) «subsurface» layer of a superdense $(10^{23}{-}10^{25}\,$cm$^{-3}$) degenerate electron gas. The double layer breaks within one picosecond through the Coulomb explosion.