Structure of an unusual tilted state of CO on Fe(001) from x-ray photoelectron diffraction

Abstract
The highly tilted α3 state of Co on Fe(001) has been studied using combined polar and azimuthal x-ray photoelectron diffraction. A more accurate structural picture is derived, with the molecule being tilted at an angle of 55°±2° with respect to the surface normal along 〈100〉 azimuths and probably occupying fourfold hollows. An estimate is also made of the vertical C distance above the Fe surface. The utility of combined θ/φ x-ray photoelectron diffraction measurements for such unusual adsorbate structures is demonstrated.