Two-temperature warm dense matter, action of ultrashort laser pulse, pump-probe technique.
We combine theoretical and experimental methods to study the processes induced by fast laser heating of metal foils. These processes reveal themselves through motion of frontal (irradiated) and rear-side foil boundaries. The irradiated targets are 0.3-2 micron thick aluminum foils deposited on much thicker (150 microns) glass plate. The instant boundary positions is measured by pump-probe technique having βΌ 40 -150 fs time and βΌ 1 nm spatial resolutions. Ultrashort laser pulse transforms a frontal surface layer with thickness dT into two-temperature (Te Ti) warm dense matter state. Its quantitative characteristics including its thickness are defined by poorly known coefficients of electron-ion energy exchange Ξ± and electron heat conductivity ΞΊ. Fast laser heating rises pressure in the dT -layer and therefore produce acoustic waves. Propagation and reflection from the frontal and rear boundaries of these waves causes the displacement Ξx(t) of boundary positions. Pressure wave profiles, and hence functions Ξx(t), depend on thickness dT . This is why the experimental detection of Ξx(t) opens a way to accurate evaluation of the coefficients Ξ± and ΞΊ.