icMRCI+Q理论研究BF~+离子电子态的光谱性质和预解离机理

采用考虑Davidson修正的内收缩多参考组态相互作用(icMRCI+Q)方法,结合相关一致基组aug-ccpV5Z和aug-cc-pV6Z,计算了BF+离子前两个离解极限B~+(~1S_g)+(~2P_u)和B+(~3P_u)+F(~2P_u)对应的14个Λ-S态(X~2Σ~+,1~2Π,2~2Π,2~2Σ~+,1~4Σ~+,1~4△,1~4Σ~-,1~2△,1~2Σ~-,3~2Σ~+,1~4Π,2~4Π,2~4Σ~+和3~2Π)和30个Ω态的势能曲线.在势能曲线的计算中,考虑了旋轨耦合效应、核价相关和标量相对论修正以及将参考能和相关能分别外推至完全基组极限.基于得到的势能曲线,获得了束缚和准束缚的12个A-S态和28个Ω态的光谱常数,并且X~2Σ~+态的光谱常数与已有的实验结果符合.此外,计算了BF分子X~1Σ~+态到BF+离子X~2Σ~+,1~2Π和2~2Σ~+态的垂直电离势和绝热电离势,并且BF~+(X~2Σ~+)←BF(X~1Σ~+)的垂直电离势和绝热电离势与相应的实验结果非常符合.由X~2Σ~+,2~2Π,1~4Σ~+,3~2Σ~+和3~2Π态和其他的激发A-S态势能曲线的交叉现象,借助于计算的旋轨耦合矩阵元,首次分析了X~2Σ~+和3~2Π态的预解离机理以及2~2Π(v′≥9),1~4Σ~+(v′≥4)和3~2Σ~+(v′≥4)的振动能级受到其他电子态的微扰.计算了30个Ω态离解极限处的相对能量,并且与实验结果十分符合.最后计算了2~2Π(v′=0—9)—X~2Σ~+,2~2Σ~+(v′=0—2)—X~2Σ~+,(3)1/2—(1)1/2~(势阱一)和(2)3/2(v′=0—9)—(1)1/2~(势阱一)跃迁的Franck-Condon因子、爱因斯坦自发辐射系数和辐射寿命.

icMRCI+Q study on spectroscopic properties and predissociation mechanisms of electronic states of BF+ cation

In this paper, we study the spectroscopic properties and predissociation mechanisms of 14 states, which come from the first two dissociation channels of the BF⁺ cation. The potential energy curves of 14 Λ-S (X²Σ⁺, 1²Π, 2²Π, 2²Σ⁺, 1⁴Σ⁺, 1⁴Δ, 1⁴Σ¹, 1²Δ, 1²Σ¹, 3²Σ⁺, 1⁴Π, 2⁴Π, 2⁴Σ⁺, and 3²Π) and corresponding 30 Ω states are calculated using the complete active space self-consistent field method, which is followed by the valence internally contracted multireference configuration interaction approach with the Davidson modification. To improve the reliability and accuracy of the potential energy curves, the core-valence correlation and scalar relativistic corrections, as well as the extrapolation of potential energy to the complete basis set limit are taken into account. The spin-orbit coupling is computed using the state interaction approach with the Breit-Pauli Hamiltonian. Based on these potential energy curves, the spectroscopic parameters and vibrational levels are determined for all the bound and quasi-bound Λ-S and Ω states. The present ground-state spectroscopic constants match well with the available experimental data. In addition, the vertical and adiabatic ionization potentials from the X¹Σ⁺ state of BF molecule to the X²Σ⁺, 1²Π, and 2²Σ⁺ states of BF⁺ cation are calculated. The results of BF⁺(X²Σ⁺) ← BF(X¹Σ⁺) ionization are in good agreement with the measurements. Various curve crossings of Λ-S states are revealed. We calculate the spin-orbit matrix elements between two interacting electronic states in the curve crossing region. With the help of present spin-orbit coupling matrix elements, we analyze the predissociation mechanisms of X²Σ⁺ and 3²Π states along with the perturbations of the nearby states to 2²Π, 1⁴Σ⁺ and 3²Σ⁺ states for the first time. The predissociation of X²Σ⁺ and 3²Π states have a chance to occur around the vibrational levels υ"=30 and υ'=0 due to spin-orbit coupling, respectively. The present results also indicate that the υ' ≥ 9 vibrational levels of 2²Π state are perturbed by the crossing states 2²Σ⁺, 1⁴Σ⁺, 1⁴Δ, 1⁴Σ¹, 1²Δ, 1²Σ¹, 3²Σ⁺, and 1⁴Π, that the υ' ≥ 4 vibrational levels of 1⁴Σ⁺ state are perturbed via the interacting states 1⁴Σ¹ and 1²Σ¹, and the great perturbations between υ' ≥ 4 vibrational levels of 3²Σ⁺ state and υ' ≥ 0 vibrational levels of 1⁴Π state. For the 30 Ω state, we also calculate the relative energies of dissociation limits compared with the lowest one matching well with the experimental ones. Finally, the Franck-Condon factors, Einstein coefficients, and radiative lifetimes are evaluated for the 2²Π (υ'=0-9)-X²Σ⁺, 2²Σ⁺ (υ'=0-2)-X²Σ⁺, (3)1/2-(1)1/2^{1st well}, and (2)3/2 (υ'=0-9)-(1)1/2^{1st well} transitions.