| 摘要: | 本研究是以266 nm 雷射為光解光源於「流動式樣品槽」( flow cell )中進行鹵化烷分子( CHBr3, CHBr2Cl, CHBrCl2 ) 的光解反應，搭配染料雷射探測其中間產物的雷射誘導螢光分光光譜 ( dispersed fluorescence spectrum ) ，並取得光解後各物種的放射光譜。在放射光譜中，看到的物種包括CH ( A2Δ, B2Σ-, C2Σ+ )，Br原子躍遷及C2的Swan Band，而在雷射誘導螢光分光光譜中，CHBrCl2的光解中可觀測到CHCl及CCl2，而在光解CHBr2Cl及CHBr3中分別可觀測到CHCl、Br2及CHBr、Br2。利用以上觀測到的物種做不同功率之雷射光源對訊號放光強度的實驗以及改變樣品槽壓力觀測訊號強弱的實驗和參考其他文獻與計算生成焓，可以推論出一溴二氯甲烷以及相關鹵化烷在266 nm的光解機制並比較三種鹵化物的光解機制之異同，顯示出這三種鹵化烷經由266 nm光解的第一個光子光解的主要路徑為斷溴原子過程。 The products and reaction intermediates in the photolysis reactions of halomethanes ( CHBrCl2, CHBr2Cl, and CHBr3 ) at 266 nm were observed in a slow flow system using nascent emission spectroscopy and laser-induced dispersed fluorescence spectroscopy. Several species including CH ( A2Δ, B2Σ-, and C2Σ+ ), excited Br atom, and C2 ( Swan band ) were successfully found in the nascent emission spectra. In the laser-induced dispersed fluorescence spectra, CHCl and CCl2 were observed in the photolysis of CHBrCl2, while in addition to Br2, CHCl and CHBr were respectively found in photolyzing CHBr2Cl and CHBr3. Based upon the power-dependence experiments, pressure dependence experiments, and other related references, the reaction mechanisms of the 266 nm photolysis of CHBrCl2, CHBr2Cl, and CHBr3 are elucidated. The similarity and differences in the photolysis reactions of these three halomethanes are clarified, and the results indicate that the main pathway of the first step in these photolysis reactions is a C-Br bond breaking process. |
