氨与甲醇混合团簇的多光子电离质谱及从头算研究  

Multiphoton ionization mass spectrum of ammonia-methanol complex cluster and ab initio calculation

作　　者：许明坤[1] 张树东[2] 孔祥和[2] 蔡廷栋[2] 姜素蓉[2] 

机构地区：[1]巢湖学院物理系,巢湖238000 [2]曲阜师范大学物理工程学院,曲阜273165

出　　处：《原子与分子物理学报》2007年第5期1049-1054,共6页Journal of Atomic and Molecular Physics

基　　金：曲阜师范大学博士科研启动基金

摘　　要：用多光子电离技术结合飞行时间质谱仪对氨与甲醇混合团簇进行了研究，在脉冲激光波长分别为266nm，355nm和532nm条件下，仅在355nm作用下观测到团簇离子，主要的电离产物为质子化的（CH3OH）n（NH3）mH^＋（n=0-6，m=0-4）混合团簇离子，且各个序列的离子强度随m的增大而减小。经分析，氨与甲醇混合团簇电离后团簇离子发生内部质子化转移反应是形成质子化团簇离子的主要原因，不同尺寸团簇离子信号强度随电离激光光强变化的光强指数曲线显示，团簇均发生四光子电离过程。应用量化计算，构造了质量数较小的几个团簇离子的可能的空间几何构型，发现二元团簇离子（CH3OH）n（NH3）mH^＋是以NH4^＋作为内核离子，再通过氢键与其它分子组合而构成团簇离子。Ammonia-methanol complex clusters have been studied by using multiphoton ionization technique and time-of-flight mass spectrometer. Laser with 266 nm,355 nm and 532 nm wavelengths were used as ionized light source, but protonated cluster ions （CH3OH）n（NH3）mH^＋（n = 0-6, m = 0- 4） were observed only when the 355 nm laser was used. The formation of （CH3OH）n（NH3）mH^＋ is mainly through proton transfer reaction intra ammonia-methanol clusters ions after laser multiphoton ionization. The curve between laser power and different size cluster ion＇s intensity indicated that the ionization undergoes a four-photon process. Some possible geometric structures of （CH3OH）n（NH3）mH^＋ with relatively small sizes were guessed using ab initio calculation method. The structures show that the NH4^＋ trends as the ion＇s center, and then it combines with other methanol or ammonia molecule to form the final stable complex cluster ions.

关 键 词：氨与甲醇混合团簇 多光子电离 飞行时间质谱 质子化团簇 从头算 

分 类 号：O657.6[理学—分析化学]