Cl2SO 光解产生的 ClSO 自由基的光谱和动力学研究,Journal of the American Chemical Society

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Cl2SO 光解产生的 ClSO 自由基的光谱和动力学研究
Journal of the American Chemical Society ( IF 14.4 ) Pub Date : 2022-10-27 , DOI: 10.1021/jacs.2c07912
Wen Chao ₁ , Gregory H Jones ₁ , Mitchio Okumura ₁ , Carl J Percival ₂ , Frank A F Winiberg ₂

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亚硫酰氯 (Cl ₂ SO) 在氯化学的广泛应用中作为常见的 Cl 原子源，但对 Cl-S 键断裂后 ClSO 自由基的反应性和光谱知之甚少。我们进行了脉冲激光光解实验，通过时间分辨紫外-可见瞬态吸收光谱在气流反应器中以 248 nm检测来自 Cl _{2 SO 光解的 ClSO。}使用 I ₂和 NO ₂进行的一些化学测试表明，在 260 和 320 nm 之间的结构化吸收带属于 ClSO 自由基，并且发生了三分子 ClSO + Cl + M → Cl ₂ SO 缔合反应。根据 EOMIP-CCSD/ano-pVQZ 计算，ClSO 带被分配给 1 ² A″ ← X² A″ 跃迁涉及 SO 键的 π* ← π 跃迁和振动进展到 1 ² A″ 状态的 SO 伸缩模式，最大横截面 = (2.0 ± 0.5) × 10 ^–18 cm ²接近 286 nm（1σ 不确定性），振动结构的平均间距为 658 cm ^–1。在 303 nm 附近监测到的 ClSO 信号的快速衰减可以拟合超过 10–90 Torr 的二阶动力学模型，从而产生有效的双分子速率系数k _Cl+ClSO = (1.48 ± 0.42) × 10 ^–11 cm ³分子^–1 s ^–1在 292 K 和 90 Torr（1σ 不确定性）。这种快速重组反应表明，含 Cl 的 SO _x物种可能在富含硫氧化物的环境（如金星大气）中充当重要的 Cl 原子库。此外，报告的紫外光谱为监测 ClSO 自由基提供了一种新方法。

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Spectroscopic and Kinetic Studies of the ClSO Radical from Cl2SO Photolysis

Thionyl chloride (Cl₂SO) serves as a common Cl atom source in widespread applications of chlorine chemistry though little is known about the reactivity and spectroscopy of the ClSO radical after a Cl–S bond cleavage. We performed a Pulsed Laser Photolysis experiment to detect ClSO from Cl₂SO photolysis at 248 nm in a gas-flow reactor by time-resolved UV–vis transient absorption spectroscopy. A few chemical tests, using I₂ and NO₂, suggested the structured absorption band between 260 and 320 nm belonged to ClSO radical and that the termolecular ClSO + Cl + M → Cl₂SO association reaction occurred. From EOMIP-CCSD/ano-pVQZ calculations, the ClSO band was assigned to the 1²A″ ← X²A″ transition involving the π* ← π transition of the SO bond and the vibrational progression to the SO stretching mode of the 1²A″ state, with a maximum cross-section = (2.0 ± 0.5) × 10^–18 cm² near 286 nm (1σ uncertainty) and an average spacing of vibrational structure of 658 cm^–1. The rapid decay of the ClSO signal monitored near 303 nm could be fit to a second-order kinetic model over 10–90 Torr, which yields an effective bimolecular rate coefficient k_Cl+ClSO = (1.48 ± 0.42) × 10^–11 cm³ molecule^–1 s^–1 at 292 K and 90 Torr (1σ uncertainty). This fast recombination reaction suggests that Cl-containing SO_x species might act as significant Cl atom reservoirs in sulfur oxide-rich environments such as Venus’ atmosphere. Moreover, the reported UV spectrum provides a new means for monitoring the ClSO radicals.

更新日期：2022-10-27

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