9 - 3
Transpector MPH Operating Manual
Focus Lens
The focus lens is a conductive aperture located next to, and usually biased
negatively with respect to, the anode. Its purpose is to draw the ions out of
the anode, form them into a beam, and focus them into the next lens
element.
Fragment Ion
A fragment ion is an ion with fewer atoms than the parent gas molecule
from which the ion is produced. The mass of the fragment ion is always
less than that of the parent ion.
Fragmentation Factor
The fragmentation factor is the fraction of the total ions produced from a
specified substance which have a given mass. The sum of the
fragmentation factors for all of the ions produced from a specified
substance is equal to one.
Fragmentation Pattern
The fragmentation pattern is the pattern of ion masses and intensities
produced by electron bombardment of a specified gas species as
transmitted by the mass filter, detected and recorded.
Gain (Electron Multiplier)
The gain of an electron multiplier is the ratio of incident ion current to
electron current output. The gain of the multiplier is a strong function of the
bias potential applied across it.
Ion
An ion is a molecule or atom which has either lost or added one or more
electrons. Those molecules which have lost electrons are positive ions.
Those molecules which have added electrons are negative ions.
Ion Current
An ion current is the rate of flow of electrical charge associated with the
flow of ions.
Ion Energy
The ion energy is the kinetic energy associated with a beam of ions. It is
equal to the potential difference across which the ion beam is accelerated
(or decelerated) times the charge on the ion, and is typically measured in
electron volts (eV). Specifically, in a quadrupole mass spectrometer, it is
the kinetic energy, along the axis, of the ions as they pass through the
mass filter. The ion energy is approximately equal to the anode potential
minus the quadrupole center voltage time the ionic charge.
Ion Source
The ion source is that part of a mass spectrometer in which neutral gas
molecules or atoms are ionized by electron bombardment.
To Next Page
Loading...
