I_(2)^(+)离子低能电子态的计算和光谱研究

Computational and spectroscopic investigation of two lowest electronic states of I_(2)^(+)

采用高精度从头算方法对I_(2)^(+)离子最小的四个Ω子态(X^(2)Π_(3/2,g),X^(2)Π_(1/2,g),A^(2)Π_(3/2,u)和A^(2)Π_(1/2,u))进行了研究,并与实验获得的高分辨率吸收光谱进行了比较。首先利用多参考组态相互作用(MRCI)方法计算了四个Ω电子态的势能曲线,求解了一维径向薛定谔方程,并推导出各电子态的振动-转动能级。随后利用拟合获得的相应光谱参数和计算得到的跃迁偶极矩矩阵元,计算了A^(2)Π_(3/2,u)-X^(2)Π_(3/2,g)系统的υ′=11−19和υ″=1−5的45个带的跃迁强度,并计算了A^(2)Π_(3/2,u)态的υ′=11−19振动能级的辐射寿命。最后,计算给出了I_(2)^(+)的A^(2)Π_(1/2,u)Ω子态的较高振动能级的预解离寿命,并讨论了其预离解机理。

Four lowestΩsubstates(X^(2)Π_(3/2,g),X^(2)Π_(1/2,g),A^(2)Π_(3/2,u) and A^(2)Π_(1/2,u))of the I_(2)^(+) cation are studied by high-precision ab initio calculations,and the calculated results are compared with the experimental high-resolution spectra of literatures.Firstly,the potential energy curves of the fourΩsubstates are calculated using the multi-reference configuration interaction(MRCI)method,and the rovibrational levels of these electronic states are derived by solving the radial Schrodinger rovibrational equation.Then,¨molecular constants are obtained by fitting energy levels to a spectroscopic model,and based on the fitted spectroscopic constants and calculated transition dipole moment matrix elements,line strengths of vibronic bands in the A^(2)Π_(3/2,u)-X^(2)Π_(3/2,g) system for 45 bands withυ′=11−19 andυ″=1−5 have been derived,and the Einstein A coefficients are employed to compute radiative lifetimes of theυ′=11−19 vibrational levels of the A^(2)Π_(3/2,u) state.Finally,based on the calculated predissociation lifetimes of the higher vibrational levels,the predissociation mechanism of the A^(2)Π_(1/2,u) state is discussed.