高靈敏度溴化亞甲基之分光光譜與溴仿光解之放射光譜研究; High Resolution Dispersed Fluorescence Spectra of Bromomethylene and Emission Spectra of Photodissociation of Bromoform

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题名:	高靈敏度溴化亞甲基之分光光譜與溴仿光解之放射光譜研究;High Resolution Dispersed Fluorescence Spectra of Bromomethylene and Emission Spectra of Photodissociation of Bromoform
作者:	張衛忠;Wei-Zhung Chang
贡献者:	化學研究所
关键词:	螢光光譜;溴化亞甲基;溴仿光解;Photodissociation of Bromoform;Bromomethylene;Dispersed Fluorescence Spectra
日期:	2005-06-16
上传时间:	2009-09-22 10:13:18 (UTC+8)
出版者:	國立中央大學圖書館
摘要:	溴化亞甲基分子(monochloromethylene, HCBr)為有機、大氣及材料化學中相當重要的反應中間物。但是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，而且無法由實驗結果精確地得知單重態(X1A')與三重態(a3A")之能階差(singlet-triplet energy gap, ΔEST)值。在本實驗中利用高壓直流放電技術結合超音速自由噴射分子束裝置，並且利用增強式電荷偶極裝置(ICCD)，取得了高靈敏度的HCBr/DCBr自由基的螢光分光光譜。在實驗中得到了HCBr/DCBr更多的基態振動能階資訊，首次得到C-H/C-D的振動頻率，以及首次觀測到放射至三重態的譜線。也確定了HCBr/DCBr三個振動量子態的基本頻率。藉由分析C-Br的振動頻率，C-Br在基態的鍵能為較弱的，且其非簡諧常數較大。實驗的另外一部份為光解溴仿之放光光譜，紫外光光解溴仿的反應機構尚未確定。在本實驗中利用266 nm的雷射光來光解溴仿，藉由其放光分光光譜，來確定產物為何，並且推測其反應機構。藉由分析以266 nm光解CHBr3/CDBr3取得的放光光譜，可以發現光解反應的產物有：CH, Br, Br2, C2等。C2的來源推測為兩分子的激發態CH碰撞所反應，或是CH和其他含碳的物種碰撞所得的。並且在實驗中推測溴仿以266 nm光解時的反應機構。 New dispersed fluorescence spectra following the excitation of several HCBr and DCBr A-X vibronic bands were successfully obtained in a supersonic free jet expansion with an intensified charge-coupled device (ICCD) detector. These dispersed fluorescence spectra show signal-to-noise ratios up to 100 and reveal the complete and detailed vibrational structure of the ground state including the previously unreported C-H/C-D stretch vibrational mode. The emission bands to the background triplet state levels in DCBr were also observed for the first time and this confirms the signlet-triplet energy gap to be 2061 cm-1 (5.89 kcal/mol) in DCBr. Emission spectra following the 266nm multiphoton photolysis of bromoform (CHBr3/CDBr3) were successfully obtained in a supersonic free jet expansion with an ICCD detector. The emission bands of Br, Br2, CH, and C2 were observed. In comparison with the enthalpies of formation of these species, the mechanism of 266nm multiphoton photolysis of bromoform is predicted.
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