摘要
本文运用角重迭模型(AOM)在考虑其全部四个参数e_σ、e_π、e_δ及e_φ的基础上首次对Eu^(3+):LaOX(X=Cl,Br,I)晶体在晶场作用下的能级劈裂进行了拟合.
Four angular overlap parameters e?????, e?????, e????? and e????? for Eu3+ ions in LaOX (X = Cl,Br,I) crystals for which the approximative point group symmetry is C4, have been calculated for the first time by making use of Angular Overlap Model(AOM). And the energy levels were fitted. The angulap overlar parameters obtained are listed in Table 2. From this we can see that the values of parameter e????????? which describes the an-tibonding effect a decrease with the increasing atomic number, that is, the order of ligands is Cl,Br,I. The order is Cl, I, Br for parameter e???????. Four angular overlap parameters are all larger for ligand Cl than for corresponding ligands Br and I. From this result we can draw a conclusion that the possibility of covalency between 4f electron and ligand is somewhat larger than the other two compounds. But there is no predo- minant order of covalency between ligands Br and I. Parameters e88888888 and e???????? also have significant contribution to the energy-level splitting and shifting. Errors will occur if we neglect them. In our calculations, the reasons for large deviation are as follows.1. Deviation of free-ion energy le els. Because we adopt the average value of experimental energy levels as the value of free-ion energy levels. For Eu3+ ions, the spectral structure is very complicated, especially for 7F5 and 7F6. The assignment of energy levels is very difficult. Hence, the error of experimental energy levels can influence the results of calculation.2. A few parameters can also cause the deviation.3. As for Eu3 + :LaOX(X = C1,Br,I) series, oxygen is also a kind of ligand besides Cl, Br and I. In our calculations we assume that the charge of all ligands is equal.In Tables 3,4, and 5, the energy levels obtained from our calculations are given, compared with experimentals. The assignments of Irreducible Representation(I.R.)are ours. They have a little difference with those of experiments (see References[10,11]).
出处
《发光学报》
EI
CAS
CSCD
北大核心
1991年第3期203-211,共9页
Chinese Journal of Luminescence
基金
国家自然科学基金
