Mass analyzers, electrostatic magnetic sector

FIGURE 7.7 The two most popular mass analyzers. The magnetic sector instrument is normally configured in tandem with an electrostatic analyzer that narrows the kinetic energy spread of the ion beam. For this reason, it is called a double-focusing spectrometer. 

The direct imaging magnetic sector mass analyzer (Fig. 3.19) has the unique property that all parts (lenses, electrostatic analyzer and magnetic sector field) of the secondary ion optics are stigmatic (comparable with light microscopes). This means that all points of the surface are simultaneously projected into the analyzer. 

Electrostatic Analyzer In magnetic-sector instruments, an electrostatic sector can be incorporated either before or after the magnet to provide energy resolution and directional focusing of the ion beam. The resolution achievable in these double-focusing instruments is sufficient to separate ions having the same nominal mass (e.g., 28 Daltons) but with different chemical formula (e.g., N2 and CO). 

If one wishes to carry ont gas-phase experiments, that is, to manipulate mass-selected ions inside the mass spectrometer, ion-trap analyzers offer the broadest arsenal of experiments including unimolecular fragmentations as well as bimolecular reactions with sufficiently volatile neutral reagents. Consequently, the choice of analyzer is also an important point. Mass analyzers use static or dynamic electric or magnetic fields to separate the ions either in time or in space. Sector-field mass analyzers use magnetic (B) and electrostatic (E) sectors to separate the ions... 

BE double-focusing mass spectrometer using a magnetic sector analyzer linked to an electrostatic... 

EB double-focusing mass spectrometer using an electrostatic analyzer linked to a magnetic sector... 

Fig. 120. Glow discharge mass spectrometry. A Sector field based instrument (a) glow discharge source (b) magnetic sector field (c) electrostatic energy analyzer (d) Daly detector (e) ...

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