In angle-resolved x-ray photoemission from the C $1s$ level of CO adsorbed on Ni(001), a peak in intensity with magnitude $\frac{I_{max}}{I_{\mathrm{back}}}\approx 1.5$ and full width at half maximum ≈ 25° is found to point along the surface normal. Single-scattering calculations for both a single CO molecule and a finite cluster verify that this peak is due to intramolecular scattering by O. The average orientation of CO is thus determined to be within 12° of normal, with an undetermined rms vibrational notion of ≲ 35°.

• Received 29 January 1979

DOI:https://doi.org/10.1103/PhysRevLett.42.1545