RESONANT FIELD-IONIZATION - A NEW IMAGING MECHANISM IN THE FIELD-ION MICROSCOPE

The high image brightness of oxygen-covered Pt and Pd surfaces obtaine d 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 argumen t for resonant field ionization. Some suggestions are made for which i maging,eases and surfaces resonant field ionization may be observed.