正一溴代烷烃的紫外光解动力学研究

摘要/Abstract

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)(C₂H5Br,n-C₃H₇Br,n-C₄H₉Br)在234及267nm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(²P_3/2)/Br^*(2P1/2).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_Br的光解动力学行为的定性解释.

关键词: 正一溴代烷烃, 飞行时间质谱, 光解动力学, 分支比

Abstract: With the deep development of environmental investigation, some alkyl bromides of higher homolog(e.g., C₂H₅Br, n-C₃H₇Br, n-C₄H₉Br) 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)(C₂H₅Br, n-C₃H₇Br, n-C₄H₉Br) at 234 and_267nm 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^*)_234nm=0.286 and φ(Br^*)_267nm=0.338 for C₂H₅Br, φ(Br^*)_234nm=0.356 and φ(Br^*)_267nm=0.294 for n-C₃H₇Br, φ(Br^*)_234nm=0.428 and φ(Br^*)_267nm=0.341 for n-C₄H₉Br.The results of φ(Br^*) clearly showed an increasing tendency with the increase of molecular complexity at 234 nm(C₂H₅Br<n-C₃H₇Br<n-C₄H₉Br), 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 C₂H₅Br and showed an increasing tendency with the increase of photon energy[φ(Br^*)_267nm< φ(Br^*)_234nm]. 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.

Key words: n-Alkyl bromide, REMPI-TOFMS, Photodissociation dynamics, Branching ratio

中图分类号:

O644.12

TrendMD:

朱荣淑, 唐碧峰, 姬磊, 唐颖, 张嵩, 王艳梅, 张冰. 正一溴代烷烃的紫外光解动力学研究. 高等学校化学学报, 2004, 25(10): 1885.

ZHU Rong-Shu, TANG Bi-Feng, JI Lei, TANG Ying, ZHANG Song, WANG Yan-Mei, ZHANG Bing . UV Photodissociation Dynamics of n-Alkyl Bromide. Chem. J. Chinese Universities, 2004, 25(10): 1885.

参考文献

[1] 　W ayne R.P..T he Chem istry of A tm o sp heres[M],N ew Yo rk:O xfo rd U n iversity,1991 [2] 　Gougou si T.,Sam artzis P.C.,K itsopou lo s T.N.et al..J.Chem.Phys.[J],1998,108:5742_5746 [3] 　H ess W.P.,Chand ler D.W.,T hom an J r.J.W.et al..Chem.Phys.[J],1992,163:277_286 [4] 　K im T.K.,Park M.S.,J um g K.H.et al..J.Chem.Phys.[J],2001,115:10745_10752 [5] 　L I Q uan-X in(李全新),RAN Q in(冉琴),CH EN Cong-X iaog(陈从香)et al..Chem.J.Ch inese U n iversities(高等学校化学学报)[J],1996,17(2):264_267 [6] 　Xu D.D.,F rancisco J.S.,J ack son M.et al..J.Chem.Phys.[J],2002,117:2578_2585 [7] 　Pfeilsticker K.,Stu rges W.T.,Sinnhuber B.M.et al..Geop hys.R es.L ett.[J],2000,27(20):3305_3308 [8] 　Carp en ter L.J.,Stu rges W.T.,P latt U.et al..J.Geop hys.R es.A tm o s.[J],1999,104:1679_1689 [9] 　W uebb les D.J.,Patten K.O.,Ko tam arth R.et al..J.Geop hys.R es.A tm o s.[J],2001,106:14551_14571 [10] 　B ridgem an C.H.,Pyle J.A.,Shallcro ss D.E.et al..J.Geop hys.R es.A tm o s.[J],2000,105:26493_26502 [11] 　W uebb les D.Ko tam arth i J.,R.,Patten K.O.et al..A tm o s.Envir.[J],1999,33:1641_1643 [12] 　W uebb les D.J.,J ain A.K.,Connell P.S.et al..A tm o s.Envir.[J],1998,32:107_113 [13] 　Eben stein W.L.,W iesenfeld J.R.,W o lk G.L.et al..Chem.Phys.L ett.[J],1978,53:185_189 [14] 　Katayanag i H.,Yoneku ira N.,Suzuk i T.et al..Chem.Phys.[J],1998,231:245_260 [15] 　Park M.S.,L ee K.W.,J ung K.H.et al..J.Chem.Phys.[J],2001,114:10368_10374 [16] 　Su to K.,Sato Y.,Kaw asak iM.et al..J.Phys.Chem.A[J],1997,101(7):1222_1226 [17] 　J ung K.H.,O h D.K.,Kw on O.S.et al..J.Pho tochem.Pho tob io .lA[J],1988,42:39_50 [18] 　J ung K.H.,O h D.K.J.Pho tochem.[J],1987,39:217_228 [19] 　M iller B.E.,Bear T..Chem.Phys.[J],1984,85:39_45 [20] 　J ung K.H.,Yoo H.S.,Hw ang J.S.et al..J.Pho tochem.[J],1983,23:289_297 [21] 　Fan Y.B.,R andall K.L.,Donald son D.J.et al..J.Chem.Phys.[J],1993,98:4700_4706 [22] 　ZHOU W ei-Dong(周卫东),SH EN G L iu-Si(盛六四),ZHAN G Yun-W u(张允武)et al..Ch inese J.Phys.Chem.(物理化学学报)[J],1999,15(10):948_951 [23] 　K im Y.S.,Kang W.K.,J ung K.H.et al..J.Chem.Phys.[J],1996,105:551_557 [24] 　Zhu Q.H.,Cao J.R.,W u X.J.et al..Chem.Phys.L ett.[J],1988,144(5_6):486_492 [25] 　Kang W.K.,J ung K.W.,J ung K.H.et al..J.Phys.Chem.[J],1994,98(6):1525_1530 [26] 　Kang W.K.,J ung K.W.,J ung K.H.et al..J.Chem.Phys.[J],1996,104(15):5815_5820 [27] 　K im u ra K.,N agaku ra S.,Sp ectr.A cta[J]1961,17:166_183 [28] 　M u lliken R.S..J.Chem.Phys.[J],1940,8:382_395 [29] 　B rum J.L.,D eshm ukh S.,Kop litz B..J.Chem.Phys.[J],1990,93(10):7504_7505 [30] 　B rum J.L.,D eshm ukh S.,Kop litz B..J.Phys.Chem.[J],1991,95(3):8676_8680 [31] 　B rum J.L.,D eshm ukh S.,Kop litz B..J.Chem.Phys.[J],1993,98(2):1178_1192 [32] 　W ang Z.R.,M athew s M.G.,Kop litz B..J.Phys.Chem.[J],1995,99:6913_6916 [33] 　A rep alli S.,P resser N.,Rob ie D.et al..Chem.Phys.L ett.[J],1985,117:64_66 [34] 　J iang Y.,A rnazziM.R.G.,Bern stein R.B.et al..Chem.Phys.[J],1986,106:171_178 [35] 　J ee Y.J.,J ung Y.J.,J ung K.H..J.Chem.Phys.[J],2001,115:9739_9746