Analyzer electrostatic sector

Most commercial ISS equipment only analyzes for charged particles, and particles that are neutralized on reflection are lost. The energy of the scattered ion is typically analyzed by an electrostatic sector analyzer or a cylindrical mirror analyzer. Ions for bombardment are provided by an ion source. Depth profiling can be done using sputter profiling techniques. 

The double-focusing combination of electrostatic- and magnetic-sector analyzers allows the inherent energy spread of the beam to be compensated for by design and ensures that there is no spread in the beam at the collector. 

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). 

Magnetic and electrostatic sectors, quadrupole, and time of flight analyzers belong to the first group, while ion trap, Orbitrap and Fourier transform ion cyclotron resonance analyzers separate ions in time. 

The first instruments used a single magnetic sector (symbol B) to effect separation of the ions. Later, the introduction of double-focusing instruments having an electrostatic sector or electrostatic analyzer (ESA, symbol E) in addition defined a standard which is still valid. 

The electrostatic sector or electrostatic analyzer (ESA) produces a radial electric field between two oppositely charged plates extending over the ESA angle ( ) (Fig. 4.21). An ion passes the ESA midway on a circular path if... 

Fig. 14. Schematic diagram for XPS measurements with a spherical sector analyzer and electrostatic lenses.

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

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) ...

Instruments using as analyzer a B,E arrangement are consequently called double-focusing mass spectrometers (see Fig. 2.5). Under these conditions, what are called first-order aberrations are overcome however, further aberrations of the ion optics are still present, due to the fringing fields present either at the magnetic or electrostatic sector levels. To reduce these undesired effects, usually electrostatic lens are placed in the field-free region of the instrument. 

Combinations of magnetic and electrostatic analyzers have been used to make instruments with high resolution capable (with appropriate calibration) of accurate mass measurements. Because they are scanning instruments, magnetic sector analyzers suffer from duty cycle limitations, as do quadrupole analyzers. Furthermore, because the scan speed of the magnetic field is proportional to resolution, additional time is required to obtain a spectrum as resolution is increased. Scanning the... 

Separation of ions according to their mass-to-charge ratio is another basic step in each mass spectral experiment. This can be done using magnetic (B) or electrostatic (E) analyzers (sector... 

Magnetic analyzers are often used in various combinations with electrostatic sectors. Sector instruments are characterized by good ion transmission. Depending on the order of these analyzers, very high resolution and wide mass ranges can be achieved. Sector instruments suffer from a relatively low scan rate, which makes their application in GC-MS and LC-MS studies somewhat limited. At the same time, some types of tandem mass spectrometry experiments with mass-selected ions can be performed only on this type of equipment. 

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