Shock Tube Measurements of the Rate Constant of the Reaction NCN + O-2
Shock Tube Measurements of the Rate Constant of the Reaction NCN + O-2
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DOI：
10.1002/kin.20932
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发表时间：
2015-09
影响因子：
1.5
通讯作者：
Nancy Faßheber;G. Friedrichs
中科院分区：
文献类型：
--
作者：
Nancy Faßheber;G. Friedrichs
本文首次用激波管法测定了相对缓慢的双分子NCN自由基反应NCN + O-2在燃烧相关条件下的速率常数。叠氮化氰（NCN3）的热分解可作为NCN自由基的清洁高温来源。在30383.11 cm（-1）处用窄带宽激光吸收检测了NCN的浓度-时间分布。在反应气体混合物中高达17% O-2的情况下进行了入射激波后的实验。在如此高的O-2摩尔分数下，有必要考虑到在实验过程中引起温度逐渐下降的O-2弛豫。此外，随着NCN3的快速分解和最初形成的单线态NCN到三重态基态的碰撞引起的系统间交叉，在100秒的时间尺度上观察到意想不到的、缓慢的三重态NCN的额外形成。这种延迟的NCN形成归因于(NCN)-N-1与O-2的快速重组，形成(NCN) -N-3加合物，作为NCN的储层。在1674 ~ 2308 K的温度范围内测量了NCN + O-2反应的速率常数。最能代表它们的是阿伦尼乌斯表达式。在216 ~ 706毫巴的压力范围内，没有观察到压力依赖性。
The rate constant of the comparably slow bimolecular NCN radical reaction NCN + O-2 has been measured for the first time under combustion relevant conditions using the shock tube method. The thermal decomposition of cyanogen azide (NCN3) served as a clean high-temperature source of NCN radicals. NCN concentration-time profiles have been detected by narrow-bandwidth laser absorption at 30383.11 cm(-1). The experiments behind incident shock waves have been performed with up to 17% O-2 in the reaction gas mixture. At such high O-2 mole fractions, it was necessary to take O-2 relaxation into account that caused a gradual decrease of the temperature during the experiment. Moreover, following fast decomposition of NCN3 and collision-induced intersystem crossing of the initially formed singlet NCN to its triplet ground state, an unexpected and slow additional formation of triplet NCN has been observed on a 100-s timescale. This delayed NCN formation was attributed to a fast recombination of (NCN)-N-1 with O-2 forming a (NCNOO)-N-3 adduct acting as a reservoir species for NCN. Rate constant data for the reaction NCN + O-2 have been measured at temperatures between 1674 and 2308 K. They are best represented by the Arrhenius expression . No pressure dependence has been observed at pressures between 216 and 706 mbar.