Peterson Kirk A, Lyons James R, Francisco Joseph S
Department of Chemistry, Washington State University, Pullman, WA 99164-4630, USA.
J Chem Phys. 2006 Aug 28;125(8):084314. doi: 10.1063/1.2222367.
Accurate calculations of the low-lying singlet and triplet electronic states of thiozone, S(3), have been carried out using large multireference configuration interaction wave functions. Cuts of the full potential energy surfaces along the stretching and bending coordinates have been presented, together with the vertical excitation spectra. The strong experimentally observed absorption around 395 nm is assigned to the 1 (1)B(2) state, which correlates to ground state products. Absorption at wavelengths shorter than 260 nm is predicted to lead to singlet excited state products, S(2) (a (1)Delta(g))+S((1)D). The spectroscopic properties of the X (3)Sigma(g) (-), a (1)Delta(g), and b (1)Sigma(g) (+) electronic states of the S(2) radical have also been accurately characterized in this work. The investigations of the low-lying electronic states were accompanied by accurate ground state coupled cluster calculations of the thermochemistry of both S(2) and S(3) using large correlation consistent basis sets with corrections for core-valence correlation, scalar relativity, and atomic spin-orbit effects. Resulting values for D(0)(S(2)+S) and SigmaD(0) for S(3) are predicted to be 61.3 and 162.7 kcal/mol, respectively, with conservative uncertainties of +/-1 kcal/mol. Analogous calculations predict the C(2v)-D(3h) (open-cyclic) isomerization energy of S(3) to be 4.4+/-0.5 kcal/mol.
利用大型多参考组态相互作用波函数对硫酮（S₃）的低能单重态和三重态电子态进行了精确计算。给出了沿拉伸和弯曲坐标的完整势能面的截面图以及垂直激发光谱。实验中在395nm附近观测到的强吸收被归属于¹¹B₂态，该态与基态产物相关。预计波长小于260nm处的吸收会导致单重激发态产物S₂(a¹Δg)+S(¹D)。在这项工作中还精确表征了S₂自由基的X³Σg⁻、a¹Δg和b¹Σg⁺电子态的光谱性质。对低能电子态的研究伴随着使用大型相关一致基组对S₂和S₃的热化学进行精确的基态耦合簇计算，并对芯价相关、标量相对论和原子自旋轨道效应进行了校正。预测S₂ + S的D₀值和S₃的ΣD₀值分别为61.3和162.7 kcal/mol，保守不确定度为±1 kcal/mol。类似的计算预测S₃的C₂ᵥ - D₃ₕ（开环）异构化能为4.4±0.5 kcal/mol。
