Angular Orientation of NH3on Ni(111) by Low-Energy Photoelectron Scattering

The azimuthal variations in the photoemission cross section for the $1e$ molecular orbital of N${\mathrm{H}}_3$ adsorbed on Ni(111) are used to identify the angular orientation of the adsorbed molecules. From comparison of experiment and theory, it is possible to determine the NH-bond directions relative to the substrate. In addition, it is found that the observed strong azimuthal anisotropy comes mainly from direct interference of emissions from the $1e$ molecular orbital rather than from backscattering off the substrate.