Department of Chemistry, University of California, Davis, Davis, California 95616, USA.
J Chem Phys. 2011 Apr 14;134(14):144304. doi: 10.1063/1.3575227.
Vacuum ultraviolet (VUV) laser pulsed field ionization-photoelectron (PFI-PE) spectroscopy has been applied to the study of the sulfur monoxide radical (SO) prepared by using a supersonically cooled radical beam source based on the 193 nm excimer laser photodissociation of SO(2). The vibronic VUV-PFI-PE bands for the photoionization transitions SO(+)(X(2)Π(1∕2); v(+) = 0) ← SO(X(3)Σ(-); v = 0); and SO(+)((2)Π(3∕2); v(+) = 0) ← SO(X(3)Σ(-); v = 0) have been recorded. On the basis of the semiempirical simulation of rotational branch contours observed in these PFI-PE bands, we have obtained highly precise ionization energies (IEs) of 83,034.2 ± 1.7 cm(-1) (10.2949 ± 0.0002 eV) and 83,400.4 ± 1.7 cm(-1) (10.3403 ± 0.0002 eV) for the formation of SO(+)(X(2)Π(1∕2); v(+) = 0) and SO(+)((2)Π(3∕2); v(+) = 0), respectively. The present VUV-PFI-PE measurement has enabled the direct determination of the spin-orbit coupling constant (A(0)) for SO(+)(X(2)Π(1∕2,3∕2)) to be 365.36 ± 0.12 cm(-1). We have also performed high-level ab initio quantum chemical calculations at the coupled-cluster level up to full quadruple excitations and complete basis set (CBS) extrapolation. The zero-point vibrational energy correction, the core-valence electronic correction, the spin-orbit coupling, and the high-level correction are included in the calculation. The IE[SO(+)(X(2)Π(1∕2,3∕2))] and A(0) predictions thus obtained are found to be in remarkable agreement with the experimental determinations.
真空紫外 (VUV) 激光脉冲场电离-光电（PFI-PE）光谱已应用于通过使用基于 193nm 准分子激光光解 SO2 的超音速冷却自由基束源制备的二氧化硫自由基（SO）的研究。记录了光致电离跃迁 SO(+)(X(2)Π(1∕2); v(+) = 0) ← SO(X(3)Σ(-); v = 0) 和 SO(+)((2)Π(3∕2); v(+) = 0) ← SO(X(3)Σ(-); v = 0)的振动 VUV-PFI-PE 带。基于观察到的这些 PFI-PE 带中旋转支轮廓的半经验模拟，我们获得了 SO(+)(X(2)Π(1∕2); v(+) = 0) 和 SO(+)((2)Π(3∕2); v(+) = 0)形成的高度精确的电离能（IE），分别为 83,034.2 ± 1.7 cm(-1) (10.2949 ± 0.0002 eV) 和 83,400.4 ± 1.7 cm(-1) (10.3403 ± 0.0002 eV)。本 VUV-PFI-PE 测量使 SO(+)(X(2)Π(1∕2,3∕2))的自旋轨道耦合常数（A(0)）能够直接确定为 365.36 ± 0.12 cm(-1)。我们还在耦合簇水平上进行了高精度从头算量子化学计算，直到完全四重激发和完全基组（CBS）外推。计算中包括零点振动能校正、芯电子校正、自旋轨道耦合和高级校正。由此获得的 IE[SO(+)(X(2)Π(1∕2,3∕2))]和 A(0)预测与实验测定结果非常吻合。
