乙硫基與二氧化氮之反應動力學研究

Abstract

本實驗為利用雷射光解－雷射誘發螢光（Laser Photolysis-Laser Induced Fluorescence）偵測乙硫基(C2H5S)和二氧化氮(NO2)的反應速率常數值。今以248nm波長的雷射光光解二硫二乙烷(C2H5SSC2H5), 產生C2H5S自由基，再以另一道雷射光激發C2H5S，而由其誘發之螢光偵測C2H5S的濃度變化，實驗條件控制為[NO2]>>[C2H5S]，使此反應在擬一級（pseudo-first-order）狀況下進行。 實驗溫度範圍為223K到296K，在室溫下（296K）下實驗得K值為 （1.05+0.15）x10-10 cm3 molecule-1 s-1，由不同壓力下的實驗數據得知此反應速率與壓力並無明顯相關性；而隨溫度的升高反應速率有增加的趨勢，但並明顯。以lnk對1/T作圖，求得k在溫度為223K到296K之阿瑞尼士表示式（Arrhenius equation）為：k = (1.9+0.2)x10-10 exp [-(170+50)/T]cm3 molecule-1 s-1，反應活化能（Ea）為1.4 kj/mol。

A Laser photolysis-Laser induced fluorescence system has been used to study the reaction kinetics of C2H5S radical with NO2. The C2H5S radicals were produced by photolyzing C2H5SSC2H5 molecules with an excimer laser output at 248nm. The concentration of C2H5S was monitored with the output of an excimer-pumped dye laser at 410.3nm. This measurements showed that the title reaction proceeds rapidly. C2H5S radicals play an important role in atmosphere chemistry. The absolute rate coefficients for the reaction of C2H5S + NO2 have been determined using laser photolysis-laser fluorescence technique at 296K-223K and pressure 65-484 torr. C2H5S + NO2 → Products k = (1.9+0.2)x10-10 exp [-(170+50)/T]cm3 molecule-1 s-1.