本研究於室溫下流動式樣品槽中以不同波長紫外光光解碘甲烷類分子(CH3I, CH2I2, CHI3, CH2ICl)與溴甲烷類分子(CHBr3, CHBr2Cl)，調查其初始放光光譜中高激發態鹵素原子之形成機制，以釐清在過去的研究中碘原子與溴原子在生成機制上之不同。本研究經由改善實驗條件取得訊號更佳的高激發態溴原子放光光譜，因此發現到許多先前未觀測到之更高能階譜線，並以不同波長紫外光光解鹵甲烷類分子，發現高激發態溴原子要在光解波長短於273.5 nm才會產生，而且溴化甲烷類分子的趨勢一致。而高激發態碘原子則在光解波長短於276.5 nm會產生外，另外在光解波長298 nm有一共振帶會產生，所有碘化甲烷類分子有著相同的趨勢。基於本實驗的結果可推論，高激發態鹵素原子生成機制為步進式(step-by-step)吸收三光子的過程，並可能經共同反應中間物如鹵化亞甲基分子(CHX或CX2)而產生。;This work investigates the nascent emission spectra following the photolysis of iodomethanes (CH3I, CH2I2, CHI3, and CH2ICl ) and bromomethanes (CHBr3 and CHBr2Cl) at different ultraviolet wavelengths in a slow flow system at ambient temperature, and aims to resolve the discrepancy in the formation mechanisms of highly exited halogen atoms in previous studies. We have improved the experimental conditions for better atomic bromine signals and found several newly observed excited states. The photolysis of bromomethanes at different ultraviolet wavelengths shows a threshold wavelength at 273.5 nm for all bromomethanes, whereas the similar study of iodomethanes shows a threshold wavelength at 276.5 nm and a resonant band at approximately 298 nm for all iodomethanes. Based on our data, the highly excited halogen atoms are generated from a three-photon step-by-step process via a common reaction intermediate such as halomethylene (CHX or CX2).
