Abstract The X2Π g, 2Σ g+ and 2Δg states of AgI2 have been studied through benchmark ab initio CASSCF + Averaged Coupled Pair Functional (ACPF) calculations using especially developed valence basis sets to study the transition energies and equilibrium geometries. The spin–orbit (SO) effects were included through the effective hamiltonian formalism using the |ΛSΣ> ACPF energies as diagonal elements. AgI2 is a linear centrosymmetric molecule with a 2Π g ground state, in contradiction with ligand-field theory. The ACPF adiabatic excitation energies of the 2Σg+ and 2Δg states are 7344 and 26085 cm-1, respectively. A comparison of the present results with the previous ones for AgCl2 and AgBr2 shows a monotonic increase in the 2Πg-2Σg+ and 2Πg-2Δg transition energies due to a decrease of the ionic structures in the LF states as the atomic number of the halogen grows. The inclusion of the SO effects leads to a pure Ω = 3/2 X(2Πg) ground state, a Ω=1/2 (83% 2Πg+17% 2Σg+) A state, a Ω=1/2 (17% 2Π g+ 83% 2Σg+) B state, a Ω=5/2 (2Δg) C state and a Ω=3/2 (2Δg) D state. The X-A, X-B, X-C, X-D vertical transition energies are 4250, 11248, 27127 and 30441 cm-1, respectively, nearly identical to the adiabatic Te values.

中文翻译：

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AgI2 的电子光谱。从头算基准 CASSCF+对配体场状态的平均耦合对功能研究，包括自旋轨道耦合

摘要 AgI2 的 X2Π g、2Σ g+ 和 2Δg 态已通过基准从头算 CASSCF + 平均耦合对泛函 (ACPF) 计算进行了研究，使用特别开发的价基组来研究跃迁能和平衡几何形状。使用 |ΛSΣ> ACPF 能量作为对角元素，通过有效的汉密尔顿形式主义包括自旋轨道 (SO) 效应。AgI2 是一种线性中心对称分子，具有 2Π g 基态，与配体场理论相矛盾。2Σg+ 和 2Δg 态的 ACPF 绝热激发能分别为 7344 和 26085 cm-1。当前结果与 AgCl2 和 AgBr2 的先前结果的比较表明，2Πg-2Σg+ 和 2Πg-2Δg 跃迁能单调增加，这是由于随着卤素原子序数的增加，LF 态的离子结构减少。包含 SO 效应导致纯 Ω = 3/2 X(2Πg) 基态，Ω=1/2 (83% 2Πg+17% 2Σg+) A 状态，Ω=1/2 (17% 2Πg) g+ 83% 2Σg+) B 状态，Ω=5/2 (2Δg) C 状态和 Ω=3/2 (2Δg) D 状态。XA、XB、XC、XD 垂直跃迁能量分别为 4250、11248、27127 和 30441 cm-1，几乎与绝热 Te 值相同。