论文标题
通过共振非弹性X射线散射对弗兰克 - 康登模型的概括
Generalization of the Franck-Condon model for phonon excitations by resonant inelastic X-ray scattering
论文作者
论文摘要
共振非弹性X射线散射（RIX）越来越多地用于量化材料中的振动相互作用。在周期系统的情况下，这通常是通过将实验结果拟合到一个简单的荷斯坦汉密尔顿的参数化但精确的分析解决方案来完成的，该解决方案由单个电子水平组成，该电子水平与单个爱因斯坦振动模式线性耦合。在此标准框架内工作，我们考虑了该模型的次要概括的影响，即引入第二个爱因斯坦振荡器，并允许激发态势能表面的曲率与地面势能表面的曲率不同。我们发现，在RIX中间（激发）状态中发生的动力学会大大改变了在RIX最终状态中观察到的光谱特征的定量解释。当多个声子模式处于活动状态时，这使单个模式模型的使用变得复杂。在这种情况下，我们的广义模型可以原则上的代替，尽管我们发现准确的定量结果依赖于对激发态势能表面的知识，尽管这通常是未知的。
Resonant inelastic X-ray scattering (RIXS) is increasingly used to quantify vibronic interactions in materials. In the case of periodic systems, this is most often done through fitting experimental results to a parameterized, but exact analytical solution of a simple Holstein Hamiltonian that consists of a single electronic level coupled linearly to a single Einstein vibrational mode. Working within this standard framework, we consider the impact of minor generalizations of this model, namely, introducing a second Einstein oscillator, and allowing the curvature of the excited-state potential energy surface to differ from that of the ground-state potential energy surface. We find that dynamics occurring in the RIXS intermediate (excited) state considerably alter the quantitative interpretation of the spectral features observed in the RIXS final state. This complicates the use of the single mode model when multiple phonon modes are active. Our generalized model may in principle by substituted in this case, though we find that accurate quantitative results rely on knowledge of the excited-state potential energy surface, though this typically is not known.
