光解一氯二溴甲烷分子(CHBr2Cl)後所產生的溴原子，是破壞大氣層中臭氧層的主要來源之一，而由長於真空紫外光波長(>200 nm)造成的光解反應之相關研究是相當有限的，因此對此一光解反應的反應機制還未有定論。本研究以266 nm為光解光源，分別於「超音速自由噴射裝置」(supersonic free jet)以及「流動式樣品槽」(flow cell)中進行一氯二溴甲烷的光解反應，搭配具高靈敏度之增強式偶合電荷裝置偵測器，成功取得光解後之放射光譜。所得物種包括CH (A2Δ)、CH (B2Σ－)、CH (C2Σ＋)、Br2 (X1Σg＋)、激發態Br原子以及由兩個CH碰撞產生之C2。其中實驗數據顯示CH為三個光子過程之產物，激發態Br原子為兩個光子過程之產物以及Br2為一個光子過程之產物。參考其他實驗數據與文獻資料，可以推論出一氯二溴甲烷在266 nm的光解機構，並可和溴仿(CHBr3)的光解機構比較，顯示這兩個溴化合物其光解產物雖然類似，但其反應機構有明顯的差異。 Atmospheric bromine atoms come from the photolysis of dibromochloromethane (CHBr2Cl) is one importance source of the ozone depletion. The studies of the photolysis of CHBr2Cl at long ultraviolet wavelengths (>200 nm) are very limited, and the reaction mechanism is still unclear. The photolysis reaction of CHClBr2 at 266 nm was observed in a supersonic free jet expansion as well as in a slow flow cell. Nascent emission spectra were successfully acquired with an intensified charge-coupled device (ICCD) detector. In the emission spectra, several species include the CH (A2Δ), CH (B2Σ－), CH (C2Σ+), Br2 (X1Σg+), excited Br atom and the collisional product C2 were observed. The power-dependence experiments indicate that CH, excited Br atom and Br2 are likely the products of a three-photon process, a one-photon process and a two-photon process, respectively. Based upon our results and other related references, the reaction mechanisms of the 266 nm photolysis of CHClBr2 are elucidated. Moreover, in comparison with the photolysis of bromoform (CHBr3), in spite of the similar products of this photolysis, their reaction mechanisms are distinctively different.
