OH自由基的高精度量子化学研究

采用内收缩MRCI方法(Internally Contracted Multiconfiguration-Reference Configuration Interaction)研究了OH自由基, 计算得到其基态稳定构型的键长是0.09708 nm, 对应的实验值是0.096966 nm, 第一激发态的键长是0.10137 nm,实验值是0.10121 nm. 同时得到势能曲线PECs (Potential Energy Curve), 再分别由Murrell-Sorbie势能函数拟合计算和POLFIT程序计算得到OH自由基在基态X²Π和第一激发态A²Σ⁺时的光谱数据：平衡振动频率ω_e, 非谐性常数ω_eχ_e以及高阶修正ω_eY_e, 平衡转动常数B_e, 振转耦合系数α_e, 解离能D₀和垂直跃迁能量ν₀₀. 这些理论计算结果与最新的实验值非常吻合, 精确度比前人也有很大提高. 其中我们计算得到基态OH(X²Π)的解离能D₀＝35568.86 cm^－1, 第一激发态OH (A²Σ⁺)的解离能D₀＝18953.93 cm^－1, 从第一激发态A²Σ⁺ (ν＝0)到基态X²Π (v＝0)的垂直跃迁能ν₀₀＝32496.42 cm^－1.

Highly Accurate Quantum Chemical Study of the OH Radical

Two potential energy curves for the ground electronic state X²Π and the first excited electronic state A²Σ⁺ of OH radical have been calculated using the internally contracted multiconfiguration-reference configuration interaction (IC-MRCI) method including Davidson correction. And they were fitted to analytical potential energy functions using the Murrell-Sorbie potential function to deduce the spectroscopic parameters: equilibrium bond length R_e, rotation coupling constant ω_e, anharmonic constant ω_eχ_e, equilibrium rotation constant B_e and vibration-rotation coupling constant α_e. These constants and higher-order anharmonic constant ω_eY_e were also calculated by POLFIT. Most of the values obtained are in excellent agreement with experimental results. The calculated dissociation energy D₀ for OH(X²Π) is 35568.86 cm^－1, which is in excellent agreement with the recent experimental value (35565±30) cm^－1. The calculated dissociation energy D₀ for OH(A²Σ⁺) is 18953.93 cm^－1. The calculated vertically excited energy from the ground state X₂Π (v＝0) to the first excited state A²Σ⁺ (ν＝0) is 32496.42 cm^－1.