d^5(~6S)离子立方零场分裂及光谱的理论研究

THE THEORETICAL STUDIES FOR ABSORPTION SPECTRA AND THE CUBIC ZERO-SPLITTING OF d^5(~6S)IONS

为了克服在晶场理论中利用微扰近似公式计算d^5(~6S)离子基态立方零场分裂参量的困难,本文用O_h 点群表象的强场方案,构造了d^5电子组态在六配位O_h 对称晶场中微扰哈密顿H′[=H_(el)+H_(?)+V_(CF)(O_h)]的完全能量矩阵.用它研究了d^5离子基态立方零场分裂参量与吸收光谱.我们发现,立方零场分裂参量a 对晶场参量Dq 的依赖关系应为:a(+|Dq|)>a(-|Dq|).由于Powell 等人的能量矩阵中Dq 和ξ_d 之间存在相对位相错误而导致零场分裂参量的计算困难,本文利用正确的d^5(O_h^(?))完全能量矩阵,统一地计算了几种六配位八面体O_h 的晶场中Fe^(3+)和Mn^(2+)离子的基态立方零场分裂和d-d跃迁吸收谱.数值分析中发现,旋轨耦合常数ξ_d 及晶场参量Dq 对立方零场分裂参量有重要影响,ξ_d 取值的差异正是Fe^(3+)和Mn^(2+)络离子立方零场分裂参量巨大差别的主要原因.由理论值与实验观测结果的一致性表明,利用正确的d^5(O_h^(?))完全能量矩阵分析,可以克服Low 等人断言的简单晶场理论计算的困难.

In order to overcome difficulties existed in explaining the cubic zero field splitting(CZFS)of d^5-~6S inos by using pertur-bation approximate formula,the complete energy matrices of the perturbation Hamiltionian H'(H_(el)+H_(so)+V_(CF)of d^5-~6S ionsin O_h point group represention have been built up.From the studies of the CZFS Parameter a and the absorption spectra of d^5ions,we find that Dq Dependence of a is,a(+|Dq|)>a(-|Dq|).It is proved that the difficulties met by Powell in explain-ing the CZFS of d^5 ions are d due to an incorrect relative phase relationship between the Dq and the spin orbit coupling parameterζ_d in their method.In this paper,an unified theoretical explanation is reached for the spectra and the CZFS of the Fe^(3-) ionsand the Mn^(2-) ions in six-ligand octahedral crystal field site.From numberal analysis,we find that the CZFS is mainly influ-enced by the Dq and the ζ_(?) and bigger difference for the CZFS of Fe^(3+) ions and Mn^(2+) ions is attributed to the difference for ζ_dparameter.The theoretical predications are in very good agreement with the findings,so that the above mentioned conclusonmade by Low and powell can be refuted.