Large solid angle X-ray photoelectron intensity distributions from CO, methoxy, and formate adsorbed on Ni(110)

Adsorbed layers of CO, methoxy (CH(3)O) and formate (HCOO) on a clean Ni(110) surface are investigated by angle-resolved X-ray photoelectron spectroscopy. Large solid angle stereographic projections of C 1s or O 1s core level intensity measured for these adsorbates at 85 K show strong forward scattering enhancements that unambiguously and rather directly determine the molecular orientation, and in the case of CO, the order within the layer. CO in the (2 x 1) p2mg structure and methoxy are tilted by 20 degrees and 30 degrees relative to the normal, respectively, with the projection of the tilt in the [001] azimuth. Formate is bonded through oxygen in the bidendate configuration, aligned along the [110] azimuth; The O-C-O bond angle is determined as 124 degrees. These results are in good agreement with previous data. (C) 1998 Elsevier Science B.V. All rights reserved.