Abstract:

A new technique of picosecond time-resolved x-ray absorption spectroscopy is applied to the study of the high-temperature, volatile liquids resulting from the heating of solid foils with a femtosecond laser pulse. In particular, this method is used to study the electronic, structure and short-range atomic structure of liquid silicon and the bonding properties of liquid carbon at a variety of near-solid densities. The absorption spectra obtained by the experiment are compared to the predictions of molecular dynamics simulations. In silicon, this results in a largely successful quantitative match of experiment to a priori x-ray scattering theory. In carbon, fits of the liquid spectra to the sum of separately identifiable components allow quantitative statements about the types of bonding present in the liquid at various densities that agree in many respects with the simulation results available in the literature. The success of these methods in studying the liquid forms of silicon and carbon demonstrates their potential to study a wide range of materials under extreme conditions of temperature and pressure.