Negative molecular state formation and dissociation of molecules scattered from Ni(111) and Ni(111) + K surfaces

Molecular ions of CO, and O 2 CO 2 are scattered at grazing incidence with an energy of 400 eV from clean Ni(111) and Ni(111) + K. Most of the scattered particles are neutralized molecules and neutral dissociation products. With increasing K-coverage the yield of negative ions and the dissociation of O 2 and CO 2 increases. In the case of Co and K adsorption has little influence on the electronic interaction with the surface. The CO 2 − ions observed are identified with corresponding negative molecular ions in chemisorption experiments, the O 2 − ions are possibly related to short lived intermediates in chemisorption.