CHEMICAL-REACTIONS OF METAL CLUSTER CATIONS IN A FOURIER-TRANSFORM ION-CYCLOTRON RESONANCE MASS-SPECTROMETER

被引:23
作者
IRION, MP
SCHNABEL, P
机构
来源
BERICHTE DER BUNSEN-GESELLSCHAFT-PHYSICAL CHEMISTRY CHEMICAL PHYSICS | 1992年 / 96卷 / 09期
关键词
ADSORPTION; CHEMICAL KINETICS; FT-ICR MASS SPECTROMETRY; ION-MOLECULE REACTIONS; METAL CLUSTERS;
D O I
10.1002/bbpc.19920960902
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
Metal cluster cations are generated in an external ion source by sputtering the respective metal foil with 20 keV Xe+ primary ions and are then injected by a series of electric lenses into the analyzer cell of a home-built Fourier-Transform lon Cyclotron Resonance Mass Spectrometer (FT-ICR MS). There, they are trapped in a magnetic field of 7 T for several tens of seconds through electrostatic deceleration and pulsed addition of a bath gas. Collisions serve to remove excess kinetic as well as inner energy and cool them to nearly room temperature. By the application of a radio frequency (RF) ejection pulse, one specific ion mass may be isolated. - Chemical reactions of the stored metal cluster ions may be studied by admitting a reactive gas with a continuous leak valve. We have investigated a variety of combinations metal/gas and found often surprising size-specific effects. For some systems, the reactivity as a function of cluster size changes in an abrupt way whereas for others it varies smoothly. Transition metal clusters predominantly show dehydrogenation reactions, the degree of which depends on the nature of the metal as well as on cluster size. In addition, it is demonstrated that naked gas phase metal cluster ions may possess catalytic activity: Fe4+ ions bind up to four molecules of ethene under hydrogen elimination and liberate benzene through collision-induced dissociation at low energy. The assertion of catalysis is proven by a complex sequence of five consecutive mass spectrometry steps (an (MS)5 experiment), in which the originally trapped Fe4+ clusters actually do initiate the synthesis of benzene twice.
引用
收藏
页码:1091 / 1100
页数:10
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