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Abstract:
A Cs monolayer on a Ru(0001) substrate emits electrons when exposed to O2 molecules. As shown previously, this ‘exoelectron’ emission is essentially confined to the late stages of oxidation where a metastable O-2,ad species forms on top of the overlayer. Detailed analysis of the kinetics reveals that electron emission is coupled to dissociation of this species which proceeds with an activation energy of about 1 eV. The exoemission active sites are blocked by the chemisorbed oxygen atoms formed, but may be partly restored through another thermally activated process (associated with an activation energy of about 1.4 eV) presumably comprising rearrangement of the O atoms below the Cs overlayer.
