The theory and experiments concerned with the electron-ion thermal relaxation and melting of overheated crystal lattice constitute the subject of this paper. The physical model includes two-temperature (2T) equation of state, many-body interatomic potential, the electron-ion energy exchange, electron thermal conductivity, and optical properties of solid, liquid, and two phase solid-liquid mixture. Two-temperature hydrodynamics and molecular dynamics codes are used. An experimental setup with pump-probe technique is used to follow evolution of an irradiated target with a short time step 100 fs between the probe femtosecond laser pulses. Accuracy of measurements of reflection coefficient and phase of reflected probe light are 1% and ∼1 nm, respectively. It is found that, firstly, the electron-electron collisions make a minor contribution to a light absorption in solid Al at moderate intensities; secondly, the phase shift of a reflected probe results from heating of ion subsystem and kinetics of melting of Al crystal during 0ps<t<4 ps, where t is time delay between the pump and probe pulses measured from the maximum of the pump; thirdly, the optical response of Au to a pump shows a marked contrast to that of Al on account of excitation of d-electrons.
Applied Surface Science
- Pub Date:
- September 2009
- Physics - Optics;
- Physics - Computational Physics
- 6th International Conference on Photo-Excited Processes and Applications 9-12 Sep 2008, Sapporo, Japan, http://www.icpepa6.com, the contributed paper will be published in Applied Surface Science(2009)