The competition between electron emission and unimolecular dissociation following the absorption of a single photon is studied for small clusters of various elements. Electron emission results from either direct photoemission, observed as a series of peaks in the spectrum, or thermionic emission, giving rise to a continuous background. Depending on the energetics involved, thermionic emission is in competition with evaporation of atoms. These results are compared to the corresponding events observed for solids, where the dominant decay products are inelastically scattered photoelectrons.

• Received 1 April 1996

DOI:https://doi.org/10.1103/PhysRevLett.77.4524