Ling Caining, Liao Hong, Yuan Daofu, Chen Wentao, Tan Yuxin, Li Wantao, Yu Shengrui, Yang Xueming, Wang Xingan
Hangzhou Institute of Advanced Studies, Zhejiang Normal University, 1108 Gengwen Road, Hangzhou 311231, Zhejiang, P. R. China.
Center for Advanced Chemical Physics and Department of Chemical Physics, School of Chemistry and Materials Science, University of Science and Technology of China, 96 Jinzhai Road, Hefei 230026, Anhui, P. R. China.
Phys Chem Chem Phys. 2021 Mar 18;23(10):5809-5816. doi: 10.1039/d1cp00078k.
The state-resolved photodissociation of the CO(1Σ+) + S(1S0) photoproduct channel, formed by vacuum ultraviolet photoexcitation of OCS to a progression of the symmetric stretching vibration (ν1') in the E and F states, has been investigated by using the time-sliced velocity map ion imaging technique. The total kinetic energy release spectra and the vibrational state specific anisotropy parameters (β) were obtained based on the raw images of S(1S0) photoproducts detected in the wavelength ranges of 134.40-140.98 nm, respectively. Except for vibrational band origins, the CO(1Σ+) photoproducts are found to have more significant populations at highly vibrationally excited states as the symmetric stretching vibrational excitation of the E and F states increases. Furthermore, the vibrational-state specific β values for the CO(1Σ+) + S(1S0) channel via the E and F states both show a sudden change from negative to positive in the vicinity of moderately vibronic levels of the E and F states. This anomalous phenomenon suggests that multiple excited states with different symmetries are involved in the photoexcitation process at relatively short photolysis wavelengths due to the strong vibronic couplings existing in the higher vibronic levels of the E and F states, and the formation of CO(1Σ+) + S(1S0) photoproducts may proceed by different nonadiabatic interactions from the prepared excited states to the lower dissociative state 1Σ+, with strong dependence of the initially symmetric stretching excitation in the Rydberg-type transitions.
通过真空紫外光将OCS光激发到E态和F态的对称伸缩振动（ν1'）跃迁，形成了CO(1Σ+) + S(1S0)光产物通道，利用时间切片速度成像技术对其态分辨光解离进行了研究。分别基于在134.40 - 140.98 nm波长范围内检测到的S(1S0)光产物的原始图像，获得了总动能释放光谱和振动态特异性各向异性参数（β）。除了振动带起源外，随着E态和F态对称伸缩振动激发的增加，发现CO(1Σ+)光产物在高振动态具有更显著的布居。此外，通过E态和F态的CO(1Σ+) + S(1S0)通道的振动态特异性β值在E态和F态的中等振转能级附近均显示出从负到正的突然变化。这种异常现象表明，由于E态和F态的较高振转能级中存在强振转耦合，在相对短的光解波长下，光激发过程涉及多个具有不同对称性的激发态，并且CO(1Σ+) + S(1S0)光产物的形成可能通过从制备的激发态到较低解离态1Σ+的不同非绝热相互作用进行，在里德堡型跃迁中强烈依赖于初始对称伸缩激发。
