Development of a kinetic analysis to elucidate the dynamics chemical reactions

提出了一种新的方法来确定反应性去除和振动弛豫之间的分支比。该方法既不需要光化学参数，也不需要感兴趣的振动能级的相对检测率的信息。我们应用该方法分析了O（^1D）+CH_4和O（^1D）+NH_3反应中OH（X^2PI_i，upsiron=OMICRON-4）的激光诱导荧光（LIF）信号的时间变化曲线。OH（Upsiron）通过LIF检测，LIF通过序列Δ Upsiron =OMICRON（Upsiron^"= 0、1和2）和Δ Upsiron =-3（Upsiron ^"=3和4）的A^2 SIGMA ^+-X^2 PI_1跃迁激发。CH_4和NH_3反应脱除OH的速率常数分别为kappa（upsiron=1）= 8.4 × <-13>10 ~ <-12>3 molecule·<-1>s ~<-1>（-1）<-12>和kappa（upsiron = 2）=6.4 × 10 <-11>~ 3 molecule·<-1>s ~（-1）<-1>。OH（upsiron）+CH_4 * OH（upsiron-1）+CH_4的振动弛豫速率常数分别为kappa（upsiron=1）=4.2 × 10 ~（-3）molecule·s ~（-1）<-13>和kappa（upsiron=2）=1.3 × 10 ~<-12>（-3）molecule·<-1>s ~<-1>（-1）; OH（upsiron）+NH_3的振动弛豫速率常数分别为kappa（upsiron=1）=2.5 × 10 ~（-3）molecule·s ~（-1）<-11>和kappa（upsiron=2）=6.4 × 10 <-11>~（-3）molecule·<-1>s ~（-1）<-1>。CH_4对OH（upsiron=1）的反应速率是OH（upsiron=OMICRON）的29倍，NH_3对OH（upsiron=1）的反应速率是OH（upsiron=1）的52倍。与CH_4和NH_3反应时，反应去除OH（upsiron=2）/OH（upsiron=1）的比值分别为5.6和7.6。还发现，通过振动激发，反应过程（反应）比物理过程（弛豫）更增强。这是首次报道化学反应与振动弛豫之间的分支比的测定。

A new method has been developed to determine the branching ratios between reactive removal and vibrational relaxation. The method needs information on neither photochemical parameters nor relative detectivities of vibrational levels of interest. We applied the method to analyze the time-dependent profiles of the laser-induced fluorescence (LIF) signals of OH (X^2PI_i, upsiron=OMICRON -4) produced in the reactions O (^1D) +CH_4 and O (^1D) +NH_3. The OH (upsiron) were deteced by LIF excited via A^2SIGMA^+-X^2PI_i transitions of the sequences DELTAupsiron=OMICRON (upsiron^"=0,1, and 2) and DELTAupsiron=-3 (upsiron^"=3 and 4). The rate constants for the reactive removal of OH by CH_4 were determined to be kappa (upsiron=1) =1.8*10^<-13> and kappa (upsiron=2) =1.0*10^<-12> cm^3 molecule^<-1> s^<-1>, and those of OH (upsiron) by NH_3 were kappa upsiron=1) =8.4*10^<-12> and kappa (upsiron=2) =6.4*10^<-11> cm^3 molecule^<-1> s^<-1>. Rate constants for vibrational relaxation of OH (upsiron) +CH_4 * OH (upsiron-1) +CH_4 were kappa (upsiron=1) =4.2*10^<-13> and kappa (upsiron=2) =1.3*10^<-12> cm^3 molecule^<-1> s^<-1>, and those of OH (upsiron) +NH_3 were kappa (upsiron=1) =2.5*10^<-11> and kappa (upsiron=2) =6.4*10^<-11> cm^3 molecule^<-1> s^<-1>. Reactive removal of OH (upsiron=1) by CH_4 was 29 times faster than that for OH (upsiron=OMICRON) ; that of OH (upsiron=1) by NH_3 was accelerated by a factor of 52. The ratio of the reactive removal OH (upsiron=2) /OH (upsiron=1) was 5.6 for the reaction with CH_4, and 7.6 for that with NH_3. It has also been found that reactive processes (reactions) are more enhanced than physical processes (relaxation) by a vibrational excitation. This is the first report on the determination of the branching ratios between chemical reaction and vibrational relaxation.