Ionization Process - Inficon Transpector MPH Operating Manual

Figure 4-1 Example mass spectrum

4.1.1.1 Ionization Process

When a sufficiently energetic electron strikes a gas molecule, there are many
processes that can occur, just some of which are summarized in
Table 4-1 Electron impact ionization processes
+
XYZ + e
XYZ
XYZ
The bottom graph is a trend analysis showing the most important
masses versus time. The top graph shows the data taken during the
scan and shows the air spectra over a six decade y-axis. The
prominent peaks for air are mass 28 from Nitrogen, mass 32 from
Oxygen, mass 40 from Argon and mass 18 from water vapor.
-

+ -
+ 2e
2+ -
+ 3e
+ -
XY + Z + 2e
+ -
XY + Z + 2e
+ -
X + YZ + 2e
+ -
X + YZ + 2e
+ -
XZ + Y + 2e
+ -
XZ + Y + 2e
Transpector MPH Operating Manual
(1)
(2)
(3)
(4)
(5)
(6)
(7)
(8)
Table 4-1.
4 - 2