Initial Sticking Coefficient for Various Gases on Titanium

Initial sticking coefficient ¹
Gas 300 K (room Temp) 78 K (Liquid Nitrogen temp)
H2 0.06 0.4
D2 0.01 0.2
H2O 0.5 -
CO 0.7 0.95
N2 0.3 0.7
O2 0.8 1
CO2 0.5 0
He 0 0
Ar 0 0
CH4 0 0.05
1 For fresh film from TSP.

Order of Preferences of Gas Displacement on Titanium Films

Displaced Gas
Gas being
Pumped
CH4 N2 H2 CO O2
CH4 - No No No No
N2 Yes - No No No
H2 Yes Yes - No No
CO Yes Yes Yes - No
O2 Yes Yes Yes Yes No
i.e. Order of preference, O2, CO, H2, N2, CH4.