NEAR-EDGE X-RAY-ABSORPTION FINE-STRUCTURE IN URANIUM-COMPOUNDS
NEAR-EDGE X-RAY-ABSORPTION FINE-STRUCTURE IN URANIUM-COMPOUNDS
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DOI：
10.1103/physrevb.35.2667
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发表时间：
1987-02-15
影响因子：
3.7
通讯作者：
KRONE, W
中科院分区：
文献类型：
--
作者：
KALKOWSKI, G;KAINDL, G;KRONE, W
对于许多金属和非金属 U 系统以及一些 Th 化合物，通过透射和总电子产额技术获取的近边缘 X 射线吸收精细结构光谱在 L 3、M 3、M 4, 5、N 4, 5 和 O 4, 5 阈值下报告。在L 3 和M 3 处，观察到具有类似信息的相似光谱。虽然在金属 U 系统中，L 3 和 M 3 处的白线仅显示位置和相对峰值高度的微小变化，但在 UCl 3 和 UF 4 之间观察到≃ 4 eV 的偏移，主要代表 2 p 3/2 芯孔和 5f 配置之间库仑相互作用的差异。由于 3d-5f 和 4d-5f 跃迁直接探测未占据的 5f 态，M 4, 5 和 N 4, 5 阈值处的光谱以强吸收峰为主。由于 3d-5f 或 4d-5f 交换相互作用，未解决多重峰结构，但发现金属 U 系统中 M 4、5 峰的线宽随着 UU 距离的增加而减小≃ 20%，反映了未占据的 5f 带的变窄。另一方面，O 4、5 阈值处的光谱显示出良好解析的结构，对于 ThF 4 和 UF 4 来说，这些结构是原子的，并且可以分别通过 5 d 9 5 f 1 和 5 d 9 5 f 3 最终态的自旋轨道和交换分裂来描述。在金属 U 系统中，O 4, 5 结构变宽并部分丢失，可能是由于 5f 态的流动性更强。在 Th 金属、ThO 2、UO 2 和 UF 4 的 M 4, 5 和 O 4, 5 光谱中，在高于阈值 15 至 38 eV 的能量处观察到其他相对较弱的峰，这些峰被分配给多重散射共振。
For a number of metallic and nonmetallic U systems as well as a few Th compounds, the near-edge x-ray-absorption fine-structure spectra, taken by transmission and total-electron-yield techniques, are reported at the L 3, M 3, M 4, 5, N 4, 5, and O 4, 5, thresholds. At L 3 and M 3, similar spectra with analogous information are observed. While in the metallic U systems, the white lines at L 3 and M 3 show only minor variations in position and relative peak height, a shift of≃ 4 eV is observed between UCl 3 and UF 4, representing mainly the difference in Coulomb interaction between a 2 p 3/2 core hole and the 5f configurations. The spectra at the M 4, 5 and N 4, 5 thresholds are dominated by intense absorption peaks due to 3d-5f and 4d-5f transitions probing directly the unoccupied 5f states. No multiplet structure due to 3d-5f or 4d-5f exchange interaction is resolved, but the linewidths of the M 4, 5 peaks in the metallic U systems are found to decrease by≃ 20% with increasing UU distance, reflecting a narrowing of the unoccupied 5f bands. The spectra at the O 4, 5 thresholds, on the other hand, show well-resolved structures, which are atomiclike for ThF 4 and UF 4 and may be described by spin-orbit and exchange splitting of the 5 d 9 5 f 1 and 5 d 9 5 f 3 final states, respectively. In metallic U systems, the O 4, 5 structures are broadened and partly lost, presumably due to the more itinerant nature of the 5f states. Additional relatively weak peaks are observed in the M 4, 5 and O 4, 5 spectra of Th metal, ThO 2, UO 2, and UF 4 at energies from≃ 15 to 38 eV above threshold, which are assigned to multiple-scattering resonances.