This paper examines the influence of transition metal cations with empty nd⁰ cores on the Eu³⁺ asymmetry ratio $R=\frac{I(5_{D_0}-7_{F_2})}{I(5_{D_0}-7_{F_1})}$ and the magnitude of crystal field splitting of the ⁷F₁ manifold (ΔΕ; ⁷F₁). Two families of compounds that crystallize with the pyrochlore and zircon structures are considered. The pyrochlores under consideration have the general formula La₂M₂O₇ (M = Hf, Zr, Sn). Comparison of the Eu³⁺ optical properties indicate that $R$ increases in order La₂Sn₂O₇ < La₂M₂O₇ (M = Hf, Zr) while (ΔΕ; ⁷F₁) varies as La₂M₂O₇ (M = Hf, Zr) < La₂Sn₂O₇. The strength of M-O covalent bonding is responsible for these trends. The M-cations in La₂M₂O₇ (M = Hf, Zr) have empty nd⁰ orbitals that participate strongly in covalent bonding with oxide anions, while the covalent contribution to the Sn⁴⁺-O^2- bonding is weak due to filled Sn⁴⁺ 4d¹⁰ core. Mulliken charge calculations of the cations and anions in isostructural pyrochlore compounds are interpreted to indicate the presence of a stronger low-symmetry crystal field component that increases the asymmetry ratio in compounds with cations having empty nd^o cores. This stronger covalent bonding is also responsible for decreasing (ΔΕ; ⁷F₁). The second family of compounds under consideration crystallize in the zircon structure with the general formula YZO₄ (Z = P, V). Comparison of Mulliken charges of cations and anions in these compounds indicates strong covalent bonding in the vanadate because it contains V⁵⁺ transition metal cation with empty 3d⁰ orbital. It leads to $R$(YPO₄) < $R$(YVO₄) and [YVO₄: (ΔΕ; ⁷F₁)] < [YPO₄: (ΔΕ; ⁷F₁)]. It is concluded that in isostructural family of compounds, the covalent bonding within the crystal framework determines $R$ and (ΔΕ; ⁷F₁).

本文研究了空n d ⁰核的过渡金属阳离子对Eu ³⁺不对称率的影响$\mathrm{[R}=\frac{\mathrm{一世}（5_{d_0}-7_{F_{\mathrm{2个}}}）}{\mathrm{一世}（5_{d_0}-7_{F_{\mathrm{1个}}}）}$以及⁷ F ₁歧管的晶体场分裂幅度（ΔE; ⁷ F ₁）。考虑了两类以烧绿石和锆石结构结晶的化合物。所考虑的烧绿石的通式为La ₂ M ₂ O ₇（M  = Hf，Zr，Sn）。Eu ³⁺光学性质的比较表明$\mathrm{[R}$依次增加La ₂ Sn ₂ O ₇  <La ₂ M ₂ O ₇（M  = Hf，Zr），而（ΔΕ; ⁷ F ₁）随着La ₂ M ₂ O ₇（M  = Hf，Zr）<La ₂ Sn而变化₂ O ₇。M -O共价键的强度是造成这些趋势的原因。La ₂ M ₂ O ₇（M  = Hf，Zr）中的M-阳离子具有空n d ⁰轨道强烈参与与氧化物阴离子的共价键合，而由于填充了Sn ⁴⁺ 4d ¹⁰核，对Sn ⁴⁺ -O ²键合的共价贡献微弱。解释了同构烧绿石化合物中阳离子和阴离子的Mulliken电荷计算，表明存在更强的低对称性晶体场成分，该成分增加了带有n d ^o核为空的阳离子的化合物的不对称率。这种更强的共价键还负责降低（ΔE；⁷ F ₁）。所考虑的第二类化合物在锆石结构中以通式Y结晶Z O ₄（Z  = P，V）。这些化合物中阳离子和阴离子的Mulliken电荷的比较表明，在钒酸盐中有很强的共价键，因为它含有带有空3d ⁰轨道的V ⁵⁺过渡金属阳离子。它导致$\mathrm{[R}$（YPO ₄）<$\mathrm{[R}$（YVO ₄）和[YVO ₄：（ΔE；⁷ F ₁）] ＜[YPO ₄：（ΔE；⁷ F ₁）]。结论是，在化合物的同构族中，晶体骨架内的共价键决定了$\mathrm{[R}$和（ΔΕ; ⁷ ˚F ₁）。