Department of Chemistry and Ames Laboratory (USDOE), Iowa State University, Ames, Iowa 50011, USA.
J Chem Phys. 2010 Feb 21;132(7):074307. doi: 10.1063/1.3298376.
In the first paper of this series, a very accurate ab initio potential energy curve of the (3)Sigma(g)(-) ground state of O(2) has been determined in the approximation that all valence shell electron correlations were calculated at the complete basis set limit. In the present study, the corrections arising from core electron correlations and relativity effects, viz., spin-orbit coupling and scalar relativity, are determined and added to the potential energy curve. From the 24 points calculated on this curve, an analytical expression in terms of even-tempered Gaussian functions is determined and, from it, the vibrational and rotational energy levels are calculated by means of the discrete variable representation. We find 42 vibrational levels. Experimental data (from the Schumann-Runge band system) only yield the lowest 36 levels due to significant reduction in the transition intensities of higher levels. For the 35 term values G(v), the mean absolute deviation between theoretical and experimental data is 12.8 cm(-1). The dissociation energy with respect to the lowest vibrational energy is calculated within 25 cm(-1) of the experimental value of 41,268.2+/-3 cm(-1). The theoretical crossing between the (3)Sigma(g)(-) state and the (1)Sigma(g)(+) state is found to occur at 2.22 A and the spin-orbit coupling in this region is analyzed.
在本系列的第一篇论文中，我们在完全基组极限下计算所有价壳层电子相关的近似条件下，确定了 O(2)的 (3)Sigma(g)(-)基态的非常精确的从头算势能曲线。在本研究中，我们确定并加入了来自芯电子相关和相对论效应的修正，即自旋轨道耦合和标量相对论。从这条曲线上的 24 个点出发，我们确定了一个用偶数调谐高斯函数表示的解析表达式，并从该表达式通过离散变量表示计算出振动和转动能级。我们发现了 42 个振动能级。由于较高能级的跃迁强度显著降低，实验数据（来自舒曼-龙格带系统）仅能得出最低的 36 个能级。对于 35 个项值 G(v)，理论数据和实验数据之间的平均绝对偏差为 12.8 cm(-1)。相对于最低振动能的离解能的计算值与实验值 41,268.2+/-3 cm(-1)的偏差在 25 cm(-1)以内。我们发现 (3)Sigma(g)(-)态和 (1)Sigma(g)(+)态之间的理论交叉发生在 2.22 A 处，并分析了该区域的自旋轨道耦合。
