Ion source electron ionization

Figure Bl.7.1. Schematic diagram of an electron ionization ion source source block (1) filament (2) trap electrode (3) repeller electrode (4) acceleration region (5) focusing lens (6).

Most of these processes are very fast. Ionization happens on the low femtosecond timescale, direct bond cleavages require between some picoseconds to several tens of nanoseconds, and rearrangement fragmentations usually proceed in much less than a microsecond (Fig. 5.3 and Chap. 2.7). Finally, some fragment ions may even be formed after the excited species has left the ion source giving rise to metastable ion dissociation (Chap. 2.7). The ion residence time within an electron ionization ion source is about 1 ps. [9]... 

The quantity c nj(Nj is the concentration of analyte emerging from the last theoretical plate into the detector, so Equation [3.11] corresponds to the desired theoretical expression for Rd(V) for cases in which the chromatographic detector has a concentration dependent response (Section 4.4.8 and Appendix 4.1) UV-visible absorption detectors are an important example since their response is described by the Beer-Lambert Law, but elecirospray ion sources for mass spectrometers can also behave in this fashion in some circumstances (Section 5.3.6b). Electron ionization ion sources provide a response that is mass flux dependent (Section 4.4.8) however, for a fixed mobile phase flow rate U (volume per unit time), the conversion from c ni(N) to the mass flow rate is trivial and this distinction is not important in the discussion of the present Section although the practical imphcations are discussed in Section 5.3.6b. 

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