Paredes-Mellone O A, Stutz G E, Ceppi S A, Arneodo Larochette P, Huotari S, Gilmore K
Facultad de Matemática, Astronomía, Física y Computación (FaMAF), Universidad Nacional de Córdoba (UNC), 5000 Córdoba, Argentina. IFEG, CONICET-UNC, FaMAF, 5000 Córdoba, Argentina.
J Phys Condens Matter. 2019 Feb 6;31(5):055501. doi: 10.1088/1361-648X/aaf24c. Epub 2018 Nov 20.
The Li 1s core excitation spectra in LiH was studied by means of x-ray Raman scattering (XRS) spectroscopy in a wide range of momentum transfers q. The analysis of the near-edge region of the measured spectra in combination with q-dependent ab initio calculations of XRS spectra based on the Bethe-Salpeter equation (BSE) reveals that the prominent peak at the excitation onset arises from two main contributions, namely a pre-edge peak associated to a p-type core exciton and strong transitions to empty states near the bottom of the conduction band, which is in contrast to previous experimental studies that attributed that feature to a single excitonic peak. The p-like angular symmetry of the core exciton is supported by BSE calculations of the relative contributions to the XRS spectra from monopole and dipole transitions and by the observed decrease of its normalised intensity for increasing momentum transfers. Higher energy spectral features in the measured XRS spectra are well reproduced by BSE, as well as by real-space multiple-scattering calculations.
通过X射线拉曼散射（XRS）光谱在广泛的动量转移q范围内研究了LiH中的Li 1s芯激发光谱。将测量光谱的近边缘区域分析与基于贝特 - 萨尔皮特方程（BSE）的XRS光谱的q依赖从头算相结合，结果表明，激发起始处的突出峰来自两个主要贡献，即与p型芯激子相关的预边缘峰以及向导带底部附近空态的强跃迁，这与之前将该特征归因于单个激子峰的实验研究形成对比。芯激子的类p角对称性得到了BSE对单极和偶极跃迁对XRS光谱相对贡献的计算以及观察到的其归一化强度随动量转移增加而降低的支持。测量的XRS光谱中的高能光谱特征通过BSE以及实空间多重散射计算得到了很好的再现。
