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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Kinetics and Dynamics on the Formation of S_2(X~3Σ_g~-,a~1Δ_g) in the S(~1D) + OCS Reaction
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Kinetics and Dynamics on the Formation of S_2(X~3Σ_g~-,a~1Δ_g) in the S(~1D) + OCS Reaction

机译：S（〜1D）+ OCS反应中S_2（X〜3Σ_g〜-，a〜1Δ_g）形成的动力学和动力学

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摘要

The reaction of electronically excited sulfur S(~1D) with OCS has exothermic channels generating S2 in two electronic states X~3Σ_g~-and a~1Δ_g. The a~1Δ_g state is correlated directly to the reactants via the spin-allowed singlet surface; the X~3Σ_g~-state, on the other hand, is a product of the spin-forbidden channel. There has been no report on kinetic evidence for the simultaneous generation of the two electronic states, although the two electronic states have been detected so far. The previous studies showed that little energy was released into rotation or vibration of the S_2 products despite large heats of reactions (228 and 175 kJ mol~(-1) for generation of X_3Σ_g~-and a~1Δ_g, respectively). In the present study, S(~1D) was generated by the photolysis of OCS at 248 nm in a buffer He at 298 K, and the resulting two electronic states of S_2 (X~3Σ_g~-and a~1Δ_g) were detected with dispersed laser-induced fluorescence (LIF) via the B~3Σ_u~-X~3Σg~-and f~1Δ_u-a~1Δ_g transitions, respectively. Not only excitation but also dispersed fluorescence spectra made it possible to find a single rotational line of the vibrational level of interest. The time-resolved LIF intensities of the initial growth of the X~3Σ_g~-and a~1Δ_g states showed identical OCS pressure dependences, giving the overall rate coefficient of the S(~1D) + OCS reaction to be [3.2 ± 0.2(2σ)] × 10~(-10) cm~3 molecule~(-1) s~(-1). The simultaneous generation of the two electronic states indicates that the intersystem crossing plays a role in opening the spin-forbidden channel. As for the reaction dynamics, vibrational levels up to v = 19 of X~3Σ_g~-and 11 of a~1Δ_g have been detected, which is distinctly different from the previous studies. The reaction mechanism has been discussed on the basis of the potential energies reported so far.
机译：电子激发的硫S（〜1D）与OCS的反应具有放热通道，在两个电子状态X〜3Σ_g〜-和a〜1Δ_g下生成S2。 a〜1Δ_g状态通过允许自旋的单线态表面直接与反应物相关;另一方面，X〜3Σ_g〜状态是自旋禁止通道的乘积。尽管到目前为止已检测到两种电子状态，但尚无有关同时生成两种电子状态的动力学证据的报道。先前的研究表明，尽管反应热很高（分别产生X_3Σ_g〜-和a〜1Δ_g的反应热为228和175 kJ mol〜（-1），但S_2产物的旋转或振动释放的能量很少）。在本研究中，S（〜1D）是通过在298 K的缓冲液He中于248 nm处OCS的光解而产生的，并且检测到了S_2的两个电子态（X〜3Σ_g〜-和a〜1Δ_g）。分别通过B〜3Σ_u〜-X〜3Σg〜和f〜1Δ_u-a〜1Δ_g跃迁分散了激光诱导的荧光（LIF）。不仅激发而且分散的荧光光谱也使得找到感兴趣的振动水平的单个旋转线成为可能。 X〜3Σ_g〜-和a〜1Δ_g态初始生长的时间分辨LIF强度显示出相同的OCS压力依赖性，从而使S（〜1D）+ OCS反应的总速率系数为[3.2±0.2（ 2σ）]×10〜（-10）cm〜3分子〜（-1）s〜（-1）。两种电子状态的同时产生表明系统间交叉在打开自旋禁止通道方面发挥了作用。至于反应动力学，已经检测到振动水平高达X =3Σ_g〜-的v = 19和a〜1Δ_g高达11的振动，这与以前的研究明显不同。已经根据迄今为止报道的势能讨论了反应机理。

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