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科学家观察到压力驱动的K壳离域现象
作者:小柯机器人 发布时间:2023/5/30 13:30:32

近日,美国劳伦斯利弗莫尔国家实验室的T.Dppner与德国罗斯托克大学的M.Bethkenhagen以及英国华威大学的D. O.Gericke等人合作,并取得一项新进展。经过不懈努力,他们成功观察到了压力驱动的K壳离域现象。相关研究成果已于2023年5月24日在国际权威学术期刊《自然》上发表。

该研究团队在国家点火设施上进行了一项实验,成功生成并诊断了在超过三百亿巴压力下的物质。他们利用国家点火设施中的184束激光束使铍壳发生内爆,利用明亮的X射线闪光实现了精密成像和X射线汤姆逊散射,从而揭示了宏观条件和微观状态。实验数据清晰地显示出量子简并电子的迹象,这些电子态被压缩了30倍,温度约为两百万开尔文。在最极端的条件下,研究人员观察到了弹性散射明显减弱的现象,主要原因是K壳电子。他们将这种减弱归因于剩余K壳电子的离域。根据这一解释,从散射数据中推断的离子电荷与从头算模拟非常吻合,但高于广泛使用的解析模型的预测值。

据悉,许多天体物体中的重力压强超过1Gbar(十亿大气压),创造了接近K壳层大小的原子核间极端的近距离条件。这种接近距离的影响改变了这些紧密束缚态,使它们在一定压强以上进入离域态。这两个过程对状态方程和辐射输运有显著影响,从而影响天体物体的结构和演化。然而,我们对于这种转变的理解仍不够令人满意,并且缺乏实验数据来支持。

附:英文原文

Title: Observing the onset of pressure-driven K-shell delocalization

Author: Dppner, T., Bethkenhagen, M., Kraus, D., Neumayer, P., Chapman, D. A., Bachmann, B., Baggott, R. A., Bhme, M. P., Divol, L., Falcone, R. W., Fletcher, L. B., Landen, O. L., MacDonald, M. J., Saunders, A. M., Schrner, M., Sterne, P. A., Vorberger, J., Witte, B. B. L., Yi, A., Redmer, R., Glenzer, S. H., Gericke, D. O.

Issue&Volume: 2023-05-24

Abstract: 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.

DOI: 10.1038/s41586-023-05996-8

Source: https://www.nature.com/articles/s41586-023-05996-8

期刊信息

Nature:《自然》,创刊于1869年。隶属于施普林格·自然出版集团,最新IF:69.504
官方网址:http://www.nature.com/
投稿链接:http://www.nature.com/authors/submit_manuscript.html