Towards a New Quantum Frontier in High Energy Density Science

未来几年新设施的发展将改变我们在极端温度、密度和压力条件下探索物质的能力。高能激光器的进步，以及它们在大型自由电子激光设施（如汉堡的欧洲XFEL）中的共同位置，将很快使我们能够定期将物质驱动到超过10 Mbar的压力，并使用地球上最明亮的X射线源进行探测。在美国，LCLS-II设施的建设将首次实现独立的X射线泵，X射线探测实验。这些能力将支持在恒星内部和系外行星核心条件下，在纳米尺度和超短时间尺度上对物质进行新的实验室研究。最有趣的是，这些进展有望提供进入奇异等离子体机制的途径，在这种机制中，量子行为被转移到宏观尺度，构成了高能量密度科学的新量子前沿。在这里，我们建议开发一个实验程序来调查这一前沿。通过使用时间分辨，共振非弹性x射线散射，我们将首先开发有效的方法来测量温度和价电子结构在实验室为基础的行星天体物理实验。然后，我们的目标是在越来越高的密度，其中核心电子相互作用变得重要的系统中的时间分辨电子局域化动力学。在这种情况下，我们将研究如何这样的电子相互作用有助于减轻或抑制相变，金属有序，并支持机制驱动复杂结构的创建，如在高压缩的双金属氧化物。最后，我们的目标是探索高能量密度量子等离子体是否能够支持核心化学，即，杂化和键合的内部电子，通过寻找存在的瞬态原子间键的原分子系统，并探测其核动力学超快时间尺度。

Novel facility developments over the next few years are set to transform our ability to explore matter in extreme conditions of temperature, density and pressure. Advances in high-energy lasers, and their co-location at large-scale free-electron laser facilities, such as the European XFEL in Hamburg, will soon allow us routinely to drive matter to pressures exceeding 10 Mbar, and probe it with the brightest x-ray source on the planet. In the US, the construction of the LCLS- II facility will enable independent x-ray-pump, x-ray-probe experiments to take place for the very first time. These capabilities will support novel laboratory-based studies of matter in stellar interior and exoplanetary core conditions, at the nanoscopic scale, and on ultrashort timescales. Most intriguingly, these advances promise to provide access to exotic plasma regimes where quantum behaviour is transferred to the macroscale, constituting a new quantum frontier in high-energy- density science. Here we propose to develop an experimental program to investigate this frontier. By using time-resolved, resonant inelastic x-ray scattering, we will firstly develop efficient approaches to measuring temperatures and valence electronic structure in laboratory-based planetary astrophysics experiments. We then aim to time-resolve electron localization dynamics in systems at increasingly high densities, where core-electron interactions become important. In this context we will study how such electron interactions help mitigate or inhibit phase transitions, metallic ordering, and support mechanisms driving the creation of complex structures such as electrides at high compression. Finally, we aim to explore whether high-energy-density quantum plasmas are able to support core-chemistry, i.e., hybridization and bonding of inner-electrons, by searching for the presence of transient interatomic bonds in proto-molecular systems, and probing their nuclear dynamics on ultrafast time scales.