Two-temperature relaxation and melting after absorption of femtosecond laser pulse

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• 作者：N.A. Inogamov ; V.V. Zhakhovskii ; S.I. Ashitkov ; V.A. Khokhlov ; Yu.V. Petrov ; P.S. Komarov ; M.B. Agranat ; S.I. Anisimov ; K. Nishihara
• 关键词：Femtosecond laser ablation ; Pump– ; probe ; Optics of hot Al and Au
• 刊名：Applied Surface Science
• 出版年：2009
• 出版时间：30 September 2009
• 年：2009
• 卷：255
• 期：24
• 页码：9712-9716
• 全文大小：474 K

文摘

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  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.