Qin Yuan, Zheng Xianfeng, Song Yu, Sun Ge, Zhang Jingsong
Department of Chemistry, University of California at Riverside, Riverside, California 92521, USA.
J Chem Phys. 2022 Oct 7;157(13):134303. doi: 10.1063/5.0110977.
Photo-predissociation of SH and SD radicals in the AΣ state is investigated using the high-n Rydberg atom time-of-flight technique. By measuring the photoproduct translational energy distributions as a function of excitation wavelength, contributions from overlapping AΣ (v') ← XΠ (v″) transitions can be separated, and the H/D + S(P) photofragment yield (PFY) spectra are obtained across various rovibrational levels (SH v' = 0-7 and SD v' = 0-8) of the AΣ ← XΠ bands. The upper AΣ state vibrational levels v' = 5-7 of SH and v' = 3-8 of SD are determined for the first time. The PFY spectra are analyzed with the simulation program PGOPHER [C. M. Western, J. Quant. Spectrosc. Radiat. Transfer 186, 221 (2016)], which gives vibrational origins and linewidths of the rovibrational levels of the AΣ state. The linewidths (≥1.5 cm) of the SH AΣ v' = 3-7 and SD AΣ v' = 2-8 states are characterized for the first time in this work, demonstrating that these levels undergo rapid predissociation with lifetimes on the order of picosecond. The lifetimes of the SD AΣ v' = 0, N' = 1 and 2 levels are determined to be 247 ± 50 ns and 176 ± 60 ns by pump-probe delay measurements, respectively. The experimentally measured lifetimes are in reasonable agreement with the theoretical predictions.
利用高n里德堡原子飞行时间技术研究了AΣ态中SH和SD自由基的光预解离。通过测量光产物平动能分布随激发波长的变化，可以分离出重叠的AΣ(v')←XΠ(v″)跃迁的贡献，并获得了AΣ←XΠ带不同振转能级（SH的v' = 0 - 7和SD的v' = 0 - 8）的H/D + S(P)光碎片产率（PFY）光谱。首次确定了SH的AΣ态振动态v' = 5 - 7以及SD的v' = 3 - 8。使用模拟程序PGOPHER [C. M. Western, J. Quant. Spectrosc. Radiat. Transfer 186, 221 (2016)]对PFY光谱进行分析，该程序给出了AΣ态振转能级的振动起源和线宽。在本工作中首次对SH的AΣ v' = 3 - 7和SD的AΣ v' = 2 - 8态的线宽（≥1.5 cm）进行了表征，表明这些能级经历快速预解离，寿命约为皮秒量级。通过泵浦 - 探测延迟测量确定SD的AΣ v' = 0、N' = 1和2能级的寿命分别为247 ± 50 ns和176 ± 60 ns。实验测量的寿命与理论预测合理吻合。
