Inficon Transpector MPS, Operating Manual

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Transpector MPS Operating Manual
4.1.1.3 Electron Energy Effects
As previously discussed, the exact fragmentation pattern observed will depend on
the energy of the bombarding electrons.
Figure 4-2 graphs the number of argon
ions (of different charge states) produced per incident electron per Torr of gas
pressure as a function of electron energy.
Figure 4-2 Electron energy effects
The appearance potential (i.e., the minimum electron energy required to produce
a specific ion) for Ar
+
is 15.7 eV. The number of argon ions produced rises steeply
with energy until a maximum is reached at about 55 eV. As the electron energy
rises above this level, the rate of Ar
+
production slowly decreases.
The appearance potential for Ar
2+
is 43.5 eV, and the ion production rate does not
maximize until the electron energy exceeds 100 eV. The appearance potential for
Ar
3+
is approximately 85 eV, while the appearance potential for Ar
4+
is over 200 eV.
34 4.18
36 0.016
Cl 35 75.4
37 24.6
Ar 36 0.337
38 0.063
40 99.600
Table 4-2 Isotope ratios (continued)
Isotope Ratios
Element Mass No.
Relative
Abundance
12
10
8
6
4
2
0
N
100 200
300 400
500
Electron Energy (eV)
Ar
+
Ar
3+
x10
Ar 4+ x100
Ar
2+
From a paper by W. Bleakney, Physical Review, 36, p. 1303, published in 1930.