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Silicon dioxide layers were investigate here. Experimental investigation of electron-ion coupling and electron heat capacity of copper in warm and dense states are presented. From time-resolved x-ray absorption spectroscopy, the temporal evolution of electron temperature is obtained for non-equilibrium warm dense copper heated by an intense femtosecond laser pulse. Electron heat capacity and electron-ion coupling are inferred from the initial electron temperature and its decrease over 10?ps. Data are compared with various theoretical models. In this study, data from experment were compared with theoretical.

Samples are tested as the following: The sample is a 70?nm thick foil of copper coated with 100?nm silicon dioxide layers on both sides. Reflection and transmission measurements of the Ti:sapphire laser pulse (800?nm, 150 fs) in the experimental geometry indicate that 80?-?95% of incident laser energies are transmitted through the silicon-dioxide layer, and the absorbed laser fluences to copper sample are estimated to be 0.32?-0.60?J/cm2 depending on the pulse energies. Since the femtosecond pulse heats the sample isochorically, corresponding energy densities Ed are 3.5-?6.5?×?106?J/kg.

The characteristic of silicon dioxide was test by X-ray. The tamping silicon dioxide layers have a large band gap and prevent the copper foil from expanding on a time scale 2d/v-30?ps, where d?=?100?nm is the thickness of the tamping layer and v?~?6000?m/s is the sound speed in Silicon dioxide(SiO2) at ambient conditions. This delay of the expansion allows us to observe the equilibration dynamics of warm dense copper at a constant volume and density. X-ray Absorption Near Edge Spectroscopy (XANES) at the copper L edge is performed using broadband 70ps X-ray pulses from an undulator source. Transmitted X-rays are dispersed by a spectrometer and detected by an X-ray streak camera. Spectral and temporal resolutions are 1?eV and 2?ps, respectively. The streak camera records a series of XANES spectra during the X-ray pulse duration. The data from experment were compared with theoretical here, more results need more research.


 

 

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