Study of CO Radicals on Magnesium Oxide with Electron Paramagnetic Resonance Techniques

It has been determined that a fraction of the carbon monoxide which is adsorbed on magnesium oxide is in a paramagnetic state. Magnesium oxide was degassed at 850°C and 10−5 Torr for 16 h, cooled to room temperature, and then exposed to 150 Torr of high-purity carbon monoxide. The resulting paramagnetic spectrum grew slowly for several weeks. This paper describes the spectrum of the adsorbed CO radical (g∥=2.0021, g∂=2.0055, ax=27 G, ay=11 G, az=0 G), the probable type of site on which the molecule is adsorbed, its bonding, and the effect of evacuating at elevated temperatures.