Observation of Excited States in Ozone near the Dissociation Limit

Several calculations suggest that the lowest triplet states of ozone lie near the dissociation limit. Using electron energy-loss spectroscopy, we have observed a broad feature beginning at 1.3 eV, with a maximum at 1.65-eV energy loss. This structure is present only under large momentum-transfer conditions, indicative of the excitation of optically forbidden states. Together with the calculations, these data demonstrate that one or more excited states of ozone exist which are stable against dissociation.