本論文研究是以近紫外光為光解光源於流動式樣品槽 (flow cell) 中進行光解反應，二溴甲烷 (CH2Br2) 的光解反應主要是以 266 nm 雷射為光源，從取得的放射光譜 (nascent emission spectra) 觀測到的放光物種有 CH (A2Δ, B2Σ-, C2Σ+)、激發態溴原子及 C2 的 Swan Band。而我們也對 CH (A2Δ) 及激發態溴原子做不同雷射功率對訊號強度實驗得知兩者皆為吸收三個 266 nm 光子的產物。我們也搭配染料雷射取得雷射誘導螢光分光光譜探測是否有光解產生中間產物的存在，但未觀測到 CHBr 與 CH2 這兩個可能的中間產物。我們還採用其他波長 (280 nm，285 nm，289 nm 及 355 nm) 光源來光解溴仿、一溴二氯甲烷及二溴甲烷，從不同波長光源光解所觀測到的產物光譜來計算光解所需要的能量，可推測光解時中間產物可能會有能量重新分配的過程，並建立一個較準確的能量圖。而在 280 nm 光解溴仿時沒有觀測到溴原子的放光，確定光解產生的是基態溴原子，並藉由改變樣品槽壓力對溴原子訊號強度的實驗讓我們更清楚的瞭解 266 nm 光解溴仿與二溴甲烷產生之激發態原子的機制。最後由文獻及我們進行光解實驗所得到的結果，可以推論出 266 nm 光解二溴甲烷的光解機制，顯示二溴甲烷與溴仿一樣第一個光子光解的主要路徑為斷 C-Br 鍵的過程。 Dibomomethane (CH2Br2) is a major source of atmospheric bromine atoms that deplete the ozone layer. We studied the photolysis reaction of dibromomethane at 266 nm using nascent emission spectroscopy and laser-induced dispersed fluorescence spectroscopy in a slow flow system. In the nascent emission spectra, several excited species including CH (A2Δ, B2Σ-, and C2Σ+), atomic Br (4Po and 4Do), and C2 (d3Πg ) were observed, while the possible reaction intermediates such as CHBr or CH2 cannot be found in the emission or laser-induced dispersed fluorescent spectra. The power dependence and concentration dependence experiments were carried out to verify the multiphoton photolysis mechanism. Additionally, nascent emission spectra of the photolysis reactions at other near ultraviolet wavelengths (280 nm, 285 nm, 289 nm, and 355 nm) of bromoform (CHBr3), dichlorobromomethane (CHBrCl2), and dibromomethane (CH2Br2) were also acquired. The differences between these emission spectra at different wavelengths reveal the energies needed for the photolysis. These results shed light on the multiphoton photolysis mechanism of bromomethanes.
