Kinetic energies of ${\mathrm{Ar}}^{+}$ ions desorbed by double photoionization at 100 eV from argon layers (from 2 to 20 monolayers) condensed on platinum are measured and compared with predicted values. Unexpected low kinetic energies are explained by a relaxed Coulomb repulsion mechanism. The weakness of the high-kinetic-energy ion signal is considered to be due to the noncrossing of the bound and repulsive potential-energy curves involved in the desorption model.

The kinetic energy distribution of photodesorbed ions from multilayers of argon is analyzed at two photon excitation energies, i.e. 40 eV and 100 eV, corresponding to the formation of satellite states and double photoionization, respectively. Surprisingly, the kinetic energy release is much smaller than what is predicted from the Coulomb repulsion model.

Electronic processes responsible for the breaking of Si-H bonds on hydrogenated Si (111) surfaces are investigated using a combination of photoemission experiments and H+ ion photodesorption studies. H+ desorption is produced after Si(2p) core excitation between 100 and 112 eV. A resonant process in the valence excitation range (20–30 eV) leads also to H+ desorption. These data confirm that electronic multi-excitation rather than single electron excitation is involved in producing ion desorption.