Ion transfer optics

The voltage applied to the extraction system determines the polarity of the accelerated ions. A negative voltage is used to extract positive ions in electron ionization and in positive chemical ionization and a positive voltage to accelerate negative ions in negative chemical ionization. An ion beam of the same charge systematically 

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Because there is so little mass bias in the mass analyzer, a discussion of ion transfer optics and collectors is not presented. The ion transfer optics of the magnetic sector mass analyzer, and the collectors used for isotope ratio measurements are critical design elements in all isotope ratio mass spectrometers and recent reviews of these items can be found in Habfast... 

Fig. 4.54. Ion transfer optics and differential pumping stages to adapt an ESI source to an FT-ICR instrument. Only the ICR cell is inside the superconducting magnet. By courtesy of Bruker Daltonik, Bremen.

Figure 5.4. Schematic of a hybrid LTQ-FTICR illustrating the distance between the ion trap and the ICR cell. Shown is an expansion of the ion transfer optics and how ions separate on their way to the ICR cell and how the low-mass ions could enter the cell, be reflected at the rear of the cell, and exit the cell while waiting for the higher mass ions to enter the cell. (Courtesy of ThennoFisher Scientific.)...

Fig. 8.5. Schematic of an API interface for CEC—MS. 1, introduction of column effluent from CEC and spraying device 2, atmospheric pressure region 3, ion sampling aperture 4, atmospheric pressure to vacuum interface 5, skimmer 6, ion transfer optics (adapted from ref. [11]).

Electron impact ionization of the parent molecule is only one of several important ion formation processes in nonthermal plasmas. Secondary processes such as electron impact ionization of neutral fragments produced by dissociation of the parent molecule and ion-molecule reactions are other mechanisms contributing to the formation of plasma ions. It is interesting to compare ion abundances in a realistic plasma with the ion abundances predicted from electron impact ionization cross sections measured under single-collision conditions. Although mass spectrometry of plasma ions is a known and well-developed diagnostic method (Osher, 1965 Drawln, 1968 Schmidt et al., 1999), its application to plasmas for thin-film deposition is not very common. The main reasons are deleterious effects of insulating deposits on the ion collection orifice (which connects the mass spectrometer to the plasma) and on the ion transfer optics, which render it... 

The ion-transfer optics include at least one quadrupole (or hexa- or octopole) at elevated pressure of about 1 mbar for thermahzation of the ions, to stabiUze them for the longer analysis time. The transfer optics also essentially decouples the TOF analyzer from the ion source for high laser pulse repetition rates the transfer optics actually converts the pulsed ion source into a continuous source. Ions are either continuously transferred into the pulser region of the TOF, or accumulated and extracted discontinuously. The fast pusher then injects them into the TOF section of the instrument The maximum rate of ion injection is Umited by the transit time of the largest ion through the TOF analyzer to typically a few kHz. Unfortunately, oTOF instruments have their Umitations ... 

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