In situ transmission Fourier transform infrared (FT-IR) spectroscopy investigations of the surface chemistry of gettering common gases in vacuum systems with a common commercial flashed getter alloy as a function of temperature

Studies of gettering reactions of a commercial flashed metal alloy commonly used in vacuum electronics with common gases found in vacuum electronic systems (CO, CO2, CH4, and O2) have been carried out in situ using Fourier transform infrared spectroscopy (FT-IR) to better understand the nature of these reactions as a function of temperature. Flashed alloy was found to adsorb CO at temperatures greater than −5 ± 5 °C across a pressure range from 3 to 50 Torr of CO. Multivariate curve resolution (MCR) was needed to extract the pure component spectra and temperature profiles for signals having intensities 10-200 times less than the background. No spectral evidence for adsorbed CO2 or CH4 was observed but both CO and CO2 were found to react with the barium film at temperatures above 77 ± 5 °C forming what is likely a combination of Ba(OH)2, Sr(OH)2, and other trace metal oxides and hydroxides. Again MCR was needed to resolve the pure spectral components and temperature profiles of these highly overlapped components. The production of metal hydroxides is likely caused by the presence of H2 sorbed to the getter during the flash as low temperature, <−50 °C, experiments with O2 showed similar reaction products. In the case of CH4 no reaction is seen with the flashed alloy surface up to 120 °C. However, in the presence of what is NiO (Ni is a trace impurity in the getter) and potentially BaO, CH4 does react at temperatures greater than 55 °C to produce CO2 which in turn reacts with the alloy film as outlined above.