雙溴化亞甲基分子（dibromomethylene, CBr2），在大氣化學、材料化學以及燃燒化學中皆扮演一重要之反應中間物的角色，但因受到其單重態之電子基態以及三重態之電子激發態之spin-orbit coupings及Fermi resonance等作用力之干擾，使光譜變的複雜而難以分析。而先前的文獻受限於偵測器觀測範圍及光譜的訊雜比不良，所以對於其基態振動資訊的瞭解仍不夠完整，無法由實驗結果精確地得知單重態與三重態之能階差(signal-triplet energy gap,)值。 本實驗利用超音速自由噴射分子束及高壓直流放電裝置搭配增強式電荷耦合偵測器(ICCD)，成功取得CBr2 A state （0,13,0)(0,14,0) 能階在可見光區之新螢光分光光譜，改進光譜之訊雜比約10倍，並延伸觀測範圍由振動能量3000 cm-1至6000 cm-1。並由分析光譜完整得到基態的振動頻率、振動常數以及藉由發現在3650 cm-1之後的未知譜線來推斷三重態與單重態能差大於10 kcal/mol，其結果與理論計算相符。 The electronic spectroscopy of halomethylenes was found to be very complicated due to a combination of spin–orbit and Fermi resonance couplings among the three low-lying electronic states. We report the new dispersed fluorescence spectrum of CBr2, in which the photomultiplier tube (PMT) detector was replaced with an intensified charge-coupled device (ICCD) detector.The new dispersed fluorescence spectra showed signal-to-noise (S/N) ratios to roughly 70, and extended the scan range form the maximum red shift frequency of 3000 cm-1 to 6000 cm-1.Complete and detailed vibrational structure of the ground singlet state was observed. Vibrational parameters including fundamental frequencies, anharmonicities, and coupling constants were determined for the CBr2 A state. Additional vibrational structure starting at approximately 3650 cm-1 was observed and this indicates the singlet–triplet energy gap to be >10 kcal / mol.
