The multiplet theory of free ions combined with crystal field theory is used to study core electron excitation of perovskites. This combined method is helpful to further identify transition peaks and comprehend the transition mechanism. In this paper, the core electron excitation of Ti K edge, L2,3 edges, and M edge in SrTiO3 and PbTiO3 is studied, and the identification of peak and the analysis of spectral shape are emphasized. Especially at the M edge, we can identify the dipole and higher-order multiple transition peaks of Ti4+. At the L2,3 edges, the transition strength corresponding to the 2p3d configuration coupling affects the shape of the spectra. The correction of the crystal field can make the theoretical spectra more consistent with the experimental spectra. For the K edge in PbTiO3, by comparing the spectral shapes and energy of Ti2+, Ti3+, and Ti4+ with experiments, the spectrum is mainly composed of Ti3+ and Ti4+, and the proportion of Ti4+ is determined to be over 91%.

中文翻译：

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SrTiO3和PbTiO3的Ti K，L2,3和M边缘的研究。

将自由离子的多重态理论与晶体场理论相结合来研究钙钛矿的核心电子激发。这种组合方法有助于进一步识别跃迁峰并了解跃迁机理。本文研究了SrTiO3和PbTiO3中Ti K边缘，L2、3边缘和M边缘的核心电子激发，并着重指出了峰的识别和光谱形状的分析。特别是在M边缘，我们可以识别出Ti4 +的偶极子和高阶多重跃迁峰。在L2,3边缘，对应于2p3d配置耦合的跃迁强度会影响光谱的形状。晶体场的校正可以使理论光谱与实验光谱更加一致。对于PbTiO3中的K边缘，通过比较Ti2 +的光谱形状和能量，