Inficon Transpector MPH Operating Manual page 76

Ionization probability factors can be approximated by substituting the relative ion
gauge sensitivities for various gases.
sensitivities for some common gases.
NOTE: The data was compiled from Empirical Observations on the Sensitivity of
HINT: Actual ionization probabilities vary significantly depending on the ionizer
Table 4-5 Ionization Probabilities for some Common Substances
Substance
acetone
air
ammonia
argon
benzene
benzoic acid
bromine
butane
carbon dioxide
carbon disulfide
carbon monoxide
carbon tetrachloride
chlorobenzene
chloroethane
chloroform
chloromethane
4 - 11
Hot Cathode Ionization Type Vacuum Gauges by R. L. Summers (NASA
Technical Note NASA TN D5285, published in 1969). Similar, although
more limited, lists of ionization sensitivities can be found in the books by
O'Hanlon (Chapter 8, Section 1.1) and Drinkwine and Lichtman (Table I,
page 5).
and the electron energy. For best accuracy, measure the relative ionization
probability using a hot cathode ionization gauge (calibrated for nitrogen) to
monitor a known pressure of the substance of interest. The ratio of the
gauge reading to the known true pressure is the relative ionization
probability. To determine the true pressure, use a gauge which is gas
species independent (for example, a capacitance manometer) or a gauge
with a known sensitivity factor (for example, a spinning rotor gauge).
Relative
Ionization
Formula
Gauge
Sensitivity
(CH ) CO 3.6
3 2
1.0
NH 1.3
3
Ar 1.2
C H 5.9
6 6
C H COOH 5.5
6 5
Br 3.8
2
C H 4.9
4 10
CO 1.4
2
CS 4.8
2
CO 1.05
CCl 6.0
4
C H Cl 7.0
6 5
C H Cl 4.0
2 5
CHCl 4.8
3
CH Cl 3.1
3
Transpector MPH Operating Manual
Table 4-5 gives relative ion gauge
Substance Formula
hydrogen chloride
hydrogen fluoride
hydrogen iodide
hydrogen sulfide
krypton
lithium
methane
methanol CH
neon
nitrogen
nitric oxide
nitrous oxide
oxygen
n-pentane C
phenol C
phosphine
Relative
Ionization
Gauge
Sensitivity
HCl 1.6
HF 1.4
HI 3.1
H S 2.2
2
Kr 1.7
Li 1.9
CH 1.6
4
OH 1.8
3
Ne 0.23
N 1.0
2
NO 1.2
N O 1.7
2
O 1.0
2
H 6.0
5 12
H OH 6.2
6 5
PH 2.6
3