BeCl分子电子激发态的多参考组态相互作用计算

运用含Davidson修正的多参考组态相互作用方法,在aug-cc-pVTZ基组水平上,对BeCl分子基态和相同多重度的几个低电子激发态进行了势能扫描计算.通过群论原理确定各电子态对称性及离解极限.将其中基态(X²Σ⁺)和第一激发态(A²Π})对应的势能曲线拟合到Murrell-Sorbie解析势能函数形式,得到基态(X²Σ⁺)的离解能及主要光谱常数(括号中为文献6]提供的实验值)为D_e=3.74eV,R_e=0.18173nm(0.17970),w_e=857.4cm¹(847.2),w_ex_e=5.03cm^-1(5.14),B_e=0.7103cm^-1(0.7285),α_e=0.0059cm^-1(0.0069),第一激发态(A²Π)的D_e=3.02eV,R_e=0.18369nm(0.18211),w_e=832.7cm^-1(822.1),w_ex_e=5.93cm^-1(5.24),B_e=0.6953cm^-1(0.7094),α_e=0.0065cm^-1(0.0068),计算结果与实验值符合得较好.另外,通过Level程序求解双原子径向核运动的Schrödinger方程得到J=0时BeCl分子这两个电子态的全部振动能级.

MRCI calculations for BeCl electronic excited states

Potential energy curves (PECs)for the ground state and several low-lying electronic excited states of BeCl molecule are calculated using the multi-reference configuration interaction (MRCI)method with the basis set of aug-cc-pVTZ where the Davidson correction is considered as an approximation to full CI. The symmetries and dissociation limits for these electronic states are determined through group theory. The PECs of ground state(X²Σ⁺)and first excited state(A²Π)are fitted to the Murrell-Sorbie (MS)potential function, and from the fitting parameters the spectroscopic constants are determined to be D_e=3.74 eV, R_e=0.18173 nm(0.17970), w_e=857.4 cm^-1(847.2), w_ex_e=5.03 cm^-1(5.14), B_e=0.7103 cm^-1(0.7285), and α_e =0.0059 cm^-1(0.0069)(where the values in parentheses are the cited experimental results)for X²Σ⁺ state and D_e=3.02 eV, R_e=0.18369 nm(0.18211), w_e=832.7 cm^-1(822.1), w_ex_e=5.93 cm^-1(5.24), B_e=0.6953 cm^-1(0.7094), and α_e=0.0065 cm^-1(0.0068)for A²Π state of BeCl. All the calculation results are in good agreement with the experimental values. In addition, we use the Level program to calculate the radial Schrödinger equation of nuclear motion to obtain the vibrational levels for the X²Σ⁺ and A²Π states.