LULI, École Polytechnique, CNRS, CEA, UPMC, route de Saclay, 91128 Palaiseau, France.
Phys Rev Lett. 2012 Feb 3;108(5):055002. doi: 10.1103/PhysRevLett.108.055002. Epub 2012 Jan 30.
The evolution of the K-edge x-ray absorption near-edge spectroscopy (XANES) spectrum is investigated for an aluminum plasma expanding from the solid density down to 0.5 g/cm{3}, with temperatures lying from 5 down to 2 eV. The dense plasma is generated by nanosecond laser-induced shock compression. These conditions correspond to the density-temperature region where a metal-nonmetal transition occurs as the density decreases. This transition is directly observed in XANES spectra measurements through the progressive formation of a preedge structure for densities around 1.6 g/cm{3}. Ab initio calculations based on density functional theory and a jellium model have been efficiently tested through direct comparison with the experimental measurements and show that this preedge corresponds to the relocalization of the 3p atomic orbital as the system evolves from a dense plasma toward a partially ionized atomic fluid.
研究了从固体密度降低到 0.5 g/cm{3}、温度从 5 eV 降低到 2 eV 的情况下，铝等离子体的 K 边 X 射线吸收近边光谱（XANES）谱的演化。通过纳秒激光诱导的冲击波压缩产生了稠密等离子体。这些条件对应于金属-非金属转变发生的密度-温度区域，随着密度的降低而发生转变。通过 XANES 光谱测量直接观察到这种转变，通过在大约 1.6 g/cm{3}的密度下逐渐形成一个前沿结构来实现。基于密度泛函理论和类固体模型的从头计算通过与实验测量的直接比较得到了有效地验证，并表明该前沿对应于 3p 原子轨道的再定位，因为系统从稠密等离子体向部分电离的原子流体演化。
