Core level spectroscopy study of N2 adsorbed on (2 × 2)K/graphite

Abstract We report a study of N 2 /(2×2)K/graphite at 25 K using X-ray photoemission, X-ray absorption (XAS), ultraviolet photoemission, autoionization and Auger spectroscopies. At this temperature we found that N 2 physisorbs. Comparisons with the physisorbed system, N 2 /graphite, reveal the role played by the alkali. The molecular coverage corresponding to saturation of the first monolayer is reduced drastically by the presence of potassium. Another dramatic effect induced by the potassium is the very high binding energy of the N 1s level due to a potassium-induced change of the work function and to a less efficient image charge screening. On the other hand, XAS, autoionization and Auger data show that in the core excited state the molecule increases its interaction with the substrate to the extent that the adsorbed potassium facilitates charge transfer to neutral core-excited N 2 . This is manifested by the appearance of a new type of final state in the autoionization.