Theory of Operation
B–5
E q u i l i b r i u m C h a r g i n g T h e o r y
The equilibrium charge distribution generated by the ionizer of the
Electrospray can be represented by a theoretical model developed
by Wiedensohler [1986], which is an approximation of the Fuchs
[1963] diffusion theory for particle sizes in the submicrometer
regime.
Figure B-2 shows the measured data of Wiedensohler [1986] and
theoretical curves based on the theory of Fuchs [1963] and
calculated by Wiedensohler [1988]. The theoretically determined
charge distribution agrees well with experimental data. It can be
seen from the figure that the fraction of positively charged particles
is different from the fraction of negatively charged particles.
Table B-2 lists the fractions of particles in air that carry +1, +2, +3,
and +4 charge units.
Figure B-2
Bipolar Particle Charge Distribution in Air [Wiedensohler and Fissan, 1988]
