EPR LINE SHIFT IN CARBON DUE TO ADSORBED OXYGEN

An amorphous carbon deposit was produced on flat glass plates by evaporation of spectroscopically pure carbon rods in an argon atmosphere. Such deposits exhibit a high spin concentration. The electron spin resonance absorption line shows anistropy in g-value dependent on orientation of the plate relative to the external magnetic field, and which appears to be due to adsorbed molecular oxygen. The results indicate that oxygen is adsorbed on an argon monolayer which tightly covers the carbon. The interaction between carbon and oxygen spins occurs across the argon monolayer. The local field produced by adsorbed oxygen at the site of the carbon spin is dependent upon the orientation of the surface relative to the external magnetic field. The calculated dependence of the local field on the surface oxygen density is in good agreement with the observed line shift. From the assumed model, the diameters of the argon atom and oxygen molecule can be determined, and are found to be in good agreement with the data given in literature. © 1969.