HO_2自由基电子激发态的理论研究

A Theoretical Study of Excited States of HO_2 Radical

采用CASPT2/CASSCF方法对HO2自由基进行统计算,优化了三个电子态的稳定点几何构型,得到详细的频率数据.利用垂直激发计算确定了3个里德堡态、11个价电子态的电子结构以及在三种理论水平上(CASSCF,SS-CASPT2和MS-CASPT2)的能量信息.计算中使用了ANO-L和ANO-L+基组,验证了已知实验数据的同时,通过与其它理论计算结果的对比,揭示了应用弥散轨道系数对于该体系激发态研究的重要性.

CASSCF and CASPT2 calculations on the HO2 radical were performed in atom natural orbital basis sets（ ANO-L and ANO-L^＋ ）. The geometries for three electronic states are optimized at CASSCF level and the energies of these electronic states were located adiabatically at CASSCF, SS-CASPT2 and MS-CASPT2 level. The first excited energy were simulated as 0. 779 eV vertically and 0. 921 eV adiabatically. These data are consistent with those of the experimental values 0. 74-0. 88 eV, compared to the vertical energy of 1.12 eV from literature. Three Rydberg states and eleven valence excited states are located vertically in CASSCF, SSCASPT2 and MS-CASPT2 levels. The lowest four low-lying electronic states are 1^2A′, 2^2A′ and 3^2A′ in the order of energy which disagreed with the former confirmed order X^2A′, A^2A″ and B2A′. Through discussing the discrepancies in detail the important significance of the dispersion orbital for the title molecule are confirmed.