Association reaction of CH3 and NO: evidence for the involvement of the triplet surface
作者:Joanne W. Davies、Nicholas J. B. Green、Michael J. Pilling
DOI:10.1039/ft9918702317
日期:——
The rate constant for the CH3+ NO reaction has been measured by laser flash photolysis/absorption spectroscopy over the temperature range 296–509 K and at pressures of 25–600 Torr. The data have been analysed using a global variant of the Troe factorisation technique which provides parameters for the representation of k1(P, T) over the experimental range. In addition, a further global technique for analysing the experimental data, based on inverse Laplace transformation of k∞1(T), coupled with a master equation treatment, has been developed. The advantage of this approach is that it emphasises the relationship between the limiting high-pressure rate coefficient and the energy-dependent lifetime of the adduct. In the present reaction system, this approach enables the lowest triplet state to be implicated in the reaction; it is proposed that, following its formation, the triplet undergoes rapid intersystem crossing to the ground singlet state. The limiting rate parameters returned from the analysis are k∞1= 1.5 × 10–11 exp(–60 K/T) cm3 molecule–1 s–1, k01= 6.9 × 10–32 exp(1430 K/T) cm6 molecule–2 s–1, 〈ΔE〉down= 235 cm–1, for Ar as the diluent gas.
通过激光闪光光解/吸收光谱法,对CH3+ NO反应的速率常数在296-509 K温度范围和25-600托压力下进行了测量。数据采用Troe因子化技术的全局变体进行了分析,该技术提供了在整个实验范围内表示k1(P, T)的参数。此外,还开发了一种基于k∞1(T)的逆拉普拉斯变换并与主方程处理相结合的全球技术来分析实验数据。这种方法的优势在于它强调了极限高压速率系数与加合物能量依赖性寿命之间的关系。在当前的反应体系中,这种方法使得最低三重态在反应中的作用得以阐明;据推测,在形成后,三重态会迅速进行系统间交叉至基态单重态。分析返回的极限速率参数为k∞1= 1.5 × 10–11 exp(–60 K/T) cm3 molecule–1 s–1,k01= 6.9 × 10–32 exp(1430 K/T) cm6 molecule–2 s–1,〈ΔE〉down= 235 cm–1,以Ar作为稀释气体。