Resonant field ionization: A new imaging mechanism in the field ion microscope

The high image brightness of oxygen-covered Pt and Pd surfaces obtained in the field ion microscope with molecular oxygen as the imaging gas is explained as due to resonant field ionization. In contrast, clean and CO-covered field emitter surfaces have so far not been imaged with molecular oxygen. We present extensive calculations of field-induced adsorption based on density functional theory in the form of potential energy curves and contour plots of wave functions to make the argument for resonant field ionization. Some suggestions are made for which imaging,eases and surfaces resonant field ionization may be observed.