标题： X射线汤姆逊散射研究高度压缩的类铍离子在加热到两百万开尔文时自旋单态的稳定化 显示英文标题

标题： X-ray Thomson scattering studies on spin-singlet stabilization of highly compressed H-like Be ions heated to two million degrees Kelvin

摘要： 在美國國家點火設施（NIF）[Döppner等人，Nature{\bf 618}，270-275 (2023)]進行的實驗創造了高度壓縮的熱氫類鈹等離子體。對NIF實驗的已發表分析使用了有限$T$多原子密度泛函理論（DFT）結合分子動力學（MD）和路徑積分蒙特卡洛（PIMC）模擬。這些方法實現起來非常耗費資源，並且通常缺乏物理透明度。本文中我們 (i) 將其結果與更簡單的第一原理平均原子結果相關聯，(ii) 建立了快速數據分析的可行性，具有良好的準確性和物理透明度的提升，以及(iii) 展示NIF實驗揭示了氫類鈹離子與近鄰的高$T$自旋單態配對。我們的分析預測，在接近兩百萬開爾文溫度的壓縮密度範圍內，這種穩定性會出現。針對電子或離子的結構因子$S(k)$、雷利權重及其他對X射線湯姆森散射感興趣的量的計算結果如下。 我们发现散射波矢量$k_{sc}$为7.89 \AA $^{-1}$ 的NIF数据更符合密度为 $20\pm2$ g/cm$^3$、平均电离度为 $\bar{Z}=$ 3.25、温度为 $\simeq$ 1,800,000 K 的情况，而不是NIF团队提出的34 g/cm$^3, \bar{Z}=3.4$。 在研究小 $k_{sc}$ 数据时，离子-电子耦合模式的相关性被指出。 显示英文摘要

摘要： Experiments at the US National Ignition Facility (NIF) [D\"{o}ppner et al., Nature {\bf 618}, 270-275 (2023)] have created highly compressed hot hydrogen-like Be plasmas. Published analyses of the the NIF experiment have used finite-$T$ multi-atom density-functional theory (DFT) with Molecular dynamics (MD), and Path-Integral Monte Carlo (PIMC) simulations. These methods are very expensive to implement and often lack physical transparency. Here we (i) relate their results to simpler first-principles average-atom results, (ii) establish the feasibility of rapid data analysis, with good accuracy and gain in physical transparency, and (iii) show that the NIF experiment reveals high-$T$ spin-singlet pairing of hydrogen-like Be ions with near neighbours. Our analysis predicts such stabilization over a wide range of compressed densities for temperatures close to two million Kelvin. Calculations of structure factors $S(k)$ for electrons or ions, the Raleigh weight and other quantities of interest to X-ray Thomson scattering are presented. We find that the NIF data at the scattering wavevector $k_{sc}$ of 7.89 \AA$^{-1}$ are more consistent with a density of $20\pm2$ g/cm$^3$, mean ionization $\bar{Z}=$3.25, at a temperature of $\simeq$ 1,800,000 K than the 34 g/cm$^3, \bar{Z}=3.4$ proposed by the NIF team. The relevance of ion-electron coupled-modes in studying small $k_{sc}$ data is indicated.