Probing harpooning and dissociation in gas–surface reactions by exoemission

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and N₂O with Cs are discussed. If the molecules interact with a metal surface the nonadiabaticity is triggered by harpooning, i.e. resonant ionization and acceleration in the image field, and subsequent dissociation. From recent experiments with state-selected N₂O molecules on Cs [1] the range of harpooning reactions is extended. From exoemission of N₂O in the first excited bending mode and its suppression in the ground state, it is concluded that a molecular affinity level may be lowered by more than 3.5 eV in front of a metallic Cs surface. This is a hint that harpooning is more common than expected.