正一溴代烷烃的紫外光解动力学研究  

UV Photodissociation Dynamics of n-Alkyl Bromide

作　　者：朱荣淑[1] 唐碧峰[1] 姬磊[1] 唐颖[1] 张嵩[1] 王艳梅[1] 张冰[1] 

机构地区：[1]中国科学院武汉物理与数学研究所

出　　处：《高等学校化学学报》2004年第10期1885-1888,共4页Chemical Journal of Chinese Universities

基　　金：国家自然科学基金 (批准号 :2 9973 0 3 7)资助

摘　　要：利用共振增强多光子电离飞行时间质谱 ( REMPI-TOFMS) ,研究了长链正一溴代烷烃 R_ Br( R为正烷烃基 ) ( C2 H5Br,n-C3H7Br,n-C4 H9Br)在 2 3 4及 2 67nm附近的光解动力学 .溴碎片来源于 R_ Br的直接解离 :R_ Br→ R+Br( 2 P3/ 2 ) /Br* ( 2 P1 / 2 ) .根据测定的离子信号强度 ,得到了 Br* 与 Br的分支比 N ( Br* ) /N ( Br)及相应的相对量子产额( Br* )和( Br) .( Br* )与激光波长及分子结构显示了一定的依赖关系 .将实验结果用 CH3Br的解离模型进行拟合 ,得到了长链 R_With the deep development of environmental investigation, some alkyl bromides of higher homolog(e.g., C 2H 5Br, n-C 3H 7Br, n-C 4H 9Br) in the lower stratosphere have attracted a little attention in recent years. But the photodissociation dynamics of them have not been studied. In this work, we reported the photodissociation dynamics of n-alkyl bromides R_Br(R=n-alkyl radical)(C 2H 5Br, n-C 3H 7Br, n-C 4H 9Br) at 234 and 267 nm using resonace-enhanced multiphoton ionization (REMPI) with time-flight mass spectrometry(TOF-MS) and the goal was to study the dependencies of the relative quantum yields of φ(Br *) and φ(Br) on photon energy and the molecular complexity. The measured values of the φ(Br *) were found to be φ(Br *) 234 nm=0.286 and φ(Br *) 267 nm=0.338 for C 2H 5Br, φ(Br *) 234 nm=0.356 and φ(Br *) 267 nm=0.294 for n-C 3H 7Br, φ(Br *) 234 nm=0.428 and φ(Br *) 267 nm=0.341 for n-C 4H 9Br.The results of φ(Br *) clearly showed an increasing tendency with the increase of molecular complexity at 234 nm(C 2H 5Br<n-C 3H 7Br<n-C 4H 9Br), while the φ(Br *) at 267 nm showed a relatively little change. Simultaneously, the φ(Br *) was found to be strongly dependent on the excitation energy except for C 2H 5Br and showed an increasing tendency with the increase of photon energy[ φ(Br *) 267 nm< φ(Br *) 234 nm]. This increasing tendency of φ(Br *) with the increase of excitation energy was in good agreement with the results observed in photodissociation of n-alkyl iodides.

关 键 词：正-溴代烷烃 光解动力学 共振增强多光子电离飞行时间质谱 分支比 相对量子产额 

分 类 号：O623.21[理学—有机化学]