Nature ( IF 64.8 ) Pub Date : 2023-05-24 , DOI: 10.1038/s41586-023-05996-8 T Döppner 1 , M Bethkenhagen 2, 3 , D Kraus 2, 4, 5 , P Neumayer 6 , D A Chapman 7 , B Bachmann 1 , R A Baggott 8 , M P Böhme 5, 9, 10 , L Divol 1 , R W Falcone 4 , L B Fletcher 11 , O L Landen 1 , M J MacDonald 1 , A M Saunders 1 , M Schörner 2 , P A Sterne 1 , J Vorberger 5 , B B L Witte 2, 11 , A Yi 12 , R Redmer 2 , S H Glenzer 11 , D O Gericke 13
The gravitational pressure in many astrophysical objects exceeds one gigabar (one billion atmospheres)1,2,3, creating extreme conditions where the distance between nuclei approaches the size of the K shell. This close proximity modifies these tightly bound states and, above a certain pressure, drives them into a delocalized state4. Both processes substantially affect the equation of state and radiation transport and, therefore, the structure and evolution of these objects. Still, our understanding of this transition is far from satisfactory and experimental data are sparse. Here we report on experiments that create and diagnose matter at pressures exceeding three gigabars at the National Ignition Facility5 where 184 laser beams imploded a beryllium shell. Bright X-ray flashes enable precision radiography and X-ray Thomson scattering that reveal both the macroscopic conditions and the microscopic states. The data show clear signs of quantum-degenerate electrons in states reaching 30 times compression, and a temperature of around two million kelvins. At the most extreme conditions, we observe strongly reduced elastic scattering, which mainly originates from K-shell electrons. We attribute this reduction to the onset of delocalization of the remaining K-shell electron. With this interpretation, the ion charge inferred from the scattering data agrees well with ab initio simulations, but it is significantly higher than widely used analytical models predict6.
中文翻译:
观察压力驱动的 K 壳离域的开始
许多天体物理物体的重力压力超过 1 千兆巴(10 亿个大气压)1,2,3,形成极端条件,原子核之间的距离接近 K 壳层的大小。这种接近改变了这些紧密结合的状态,并在一定压力以上将它们驱使到离域状态4。这两个过程都会显着影响状态方程和辐射传输,从而影响这些物体的结构和演化。尽管如此,我们对这种转变的理解还远未令人满意,实验数据也很少。在这里,我们报告了在国家点火装置5中在超过 3 吉巴的压力下制造和诊断物质的实验184 束激光束使铍壳发生内爆。明亮的 X 射线闪光使精确的射线照相和 X 射线汤姆逊散射能够揭示宏观条件和微观状态。数据显示量子简并电子处于压缩 30 倍状态和大约 200 万开尔文温度的明显迹象。在最极端的条件下,我们观察到弹性散射强烈减少,这主要源于 K 壳层电子。我们将这种减少归因于剩余 K 壳层电子开始离域。通过这种解释,从散射数据推断出的离子电荷与从头算模拟非常吻合,但明显高于广泛使用的分析模型预测6。