Local electron distribution of N2 adsorbed on a Ni(111) surface probed by metastable impact electron spectroscopy

Abstract

Electron emission spectra resulting from thermal collisions of He*(23S) metastable atoms with N2 on a Ni(111) surface in the physisorbed, chemisorbed, and condensed phases were measured as well as the gas-phase spectrum. The ionization cross sections for the 3σg-, 1πu-, and 2σu-derived states depend on the orientation of N2 with respect to the metastable beam, reflecting the spatial electron distribution. Our data also show that upon chemisorption the 3σg- and 2σu-derived states are modified by mixing with each other to yield a strong charge localization. This finding indicates that, even if the metal contribution is small in the chemisorbed states, it plays a crucial role in the topology of the adsorbate wave functions.