理论研究晶体场效应和电荷转移效应对Co^(2+)的2p电子X射线L2,3吸收边光谱的影响

An In-depth Theoretical Study of Ligand Field and Charge Transfer Effects on Co_(2p)^(2+) L_(2,3)-edges X-ray Absorption Spectra

运用多重态计算方法研究了在正八面体对称性的晶体场中Co^(2+)离子的2p电子X射线L2,3吸收边光谱,研究了Co^(2+)离子和周围的配位离子之间的正八面体(Oh)晶体场效应和相应的电荷转移效应对于吸收光谱的影响.系统讨论了在多重态计算中起作用的所有物理参数对CoO和CoCl_(2)的X射线吸收光谱特性的特定影响及其物理机制.将计算得出的光谱数据和同样具有Oh对称性结构Co^(2+)离子的CoO和CoCl_(2)实验光谱数据进行了对比,在实验光谱数据中发现的特征被确定为来自不同自旋态,并且光谱强度的变化与晶体场的强度相关,揭示了其中包含的电荷转移效应.本文为低对称性复杂系统的多重态计算提供了一个基础的参考标准,可以适用于含有钴元素或其它过渡金属的复杂体系的X射线吸收光谱的理论计算.

The 2p L_(2,3)-edges X-ray absorption spectrum of Co^(2+)in octahedral(Oh)symmetric ligand field is studied theoretically via the multiplet calculation method.The octahedral symmetric crystal field and corre⁃sponding charge transfer effect between ligands and Co^(2+)cation have been investigated.All the parameters used in the multiplet calculation are discussed systematically in regards to their specific effect on X-ray absorp⁃tion features and related mechanisms.The calculated results are compared with the L-edge X-ray absorption spectra of CoO and CoCl_(2),both with the same Oh symmetrical local structure of the Co^(2+)cation.The experimen⁃tally observed multiplet spectra features are assigned to different spin states and their intensity change is rela-ted to the crystal field strength.The underlying charge transfer effect has also been revealed.This study pro⁃vides a fundamental basis for multiplet calculations of complex systems with lower symmetry associated with cobalt and other transition metals.