Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.
Proc Natl Acad Sci U S A. 2012 Jun 26;109(26):10205-9. doi: 10.1073/pnas.1200725109. Epub 2012 Jun 15.
Uranium and plutonium's 5f electrons are tenuously poised between strongly bonding with ligand spd-states and residing close to the nucleus. The unusual properties of these elements and their compounds (e.g., the six different allotropes of elemental plutonium) are widely believed to depend on the related attributes of f-orbital occupancy and delocalization for which a quantitative measure is lacking. By employing resonant X-ray emission spectroscopy (RXES) and X-ray absorption near-edge structure (XANES) spectroscopy and making comparisons to specific heat measurements, we demonstrate the presence of multiconfigurational f-orbital states in the actinide elements U and Pu and in a wide range of uranium and plutonium intermetallic compounds. These results provide a robust experimental basis for a new framework toward understanding the strongly-correlated behavior of actinide materials.
铀和钚的 5f 电子在与配体 spd 态强烈键合和靠近原子核之间处于不稳定平衡状态。这些元素及其化合物的异常性质（例如，元素钚的六种不同同素异形体）被广泛认为取决于 f 轨道占据和离域的相关属性，而这些属性缺乏定量衡量。通过使用共振 X 射线发射光谱 (RXES) 和 X 射线吸收近边结构 (XANES) 光谱，并与比热测量进行比较，我们证明了铀和钚的锕系元素以及广泛的铀和钚金属间化合物中存在多组态 f 轨道状态。这些结果为理解锕系材料的强关联行为提供了一个新的稳健实验基础。
