Principles and Instrumentation

The overall diagram of a fast atom bombardment ion source is fairly simple. It consists of three main elements i) an atom gun, ii) a sample inlet, and iii) an ion extraction system. The atom gun is made up of an evacuated chamber that encloses a plate to which a high voltage potential (nominally 8 kV) is apphed. The gas to be used for the bombardment is allowed into the chamber, through an appropriate inlet, where it is ionised by the high potential plate (see equation (22)). The ion beam so created is repelled by the same plate (at 8 kV) and, to a certain extent, regains its neutral character by electron-capture or by charge-resonance processes such as those exemplified by equations (23) and (24). 

Since the atoms do not suffer much loss in momentum they exit the atom gun and are aimed at the target where the sample is located. A high voltage plate, positioned at 90 degrees with respect to the atom beam, is used to deflect the remaining ions that have not been neutrahsed. Thus only the atom beam reaches the sample to be analysed. 

Saddle field-type ion sources are compact, simple and efficient. They have been widely adopted for this pxirpose. Their characteristics are well documented and they have been used since the early development of FAB. 

On the other hand, turning off the deflector plates, used in FAB to clean the atom beam from residual ions that have not charge-exchanged, still produces a FAB-like spectrum. Devienne and Roustan, who have performed SIMS versus FAB studies on organics, did not report on the evidence, or lack thereof of a close similarity between the techniques and more recent SIMS studies indicate that it is possible to obtain SIMS results that are similar to those obtained by FAB. 

It is not expected that the types of analyser and detector used in the mass spectrometer should be critical for the successful recording of FAB spectrum and thus far, the hterature supports this statement. Single- and double- 

Buchi et al. estimated that the Ohmic resistance responds to a current change in less than 0.5 ns, while the charge transfer resistance responds to a current change in 

The time constant during the discharge of an electrochemical process can be estimated by the following equation according to Newman [29]  

Because the time constants of the voltage decay in these measurements are so small, a fast digital oscilloscope is typically used for the measurement. It is connected to the anode and the cathode current collectors of the cell. 

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Guilhaus M 1995 Principles and instrumentation in time-of-flight mass spectrometry physical and instrumental concepts J. Mass Spectrom. 30 1519-32... 

An overview of the principles and instrumentation of MS, its powerful ability and utility in the identification, structural characterization and quantitation of analytes, together with applications in cultural heritage, are presented in this chapter. 

There are many types of mass spectrometer, each having special design features, some offering very sophisticated modes of analysis and these details will not be described here. Rather, the fundamental principles and instrumental aspects associated with the technique in general are covered. More detailed information is available in specialist books or instrument manufacturers publications. 

Development principles and instruments that can easily track the sources of hydrocarbons that are reactive in the production of ozone and hydrocarbons that are reactive in the production of particles. 

Mass Spectrometry in Bioanalysis -Methods, Principles and Instrumentation... 

Tran, C. D. (2003), Infrared multispectral imaging Principles and instrumentation, Appl. Spectrosc. Rev., 38,133-153. 

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