DISSOCIATIVE SCATTERING OF POLYATOMIC IONS FROM A LIQUID SURFACE - CF3+ ON A PERFLUOROPOLYETHER FILM

The dissociative scattering of CF3+ ions from a liquid insulating perf luorinated polyether surface was explored in the incident energy range 100-500 eV. We have measured the angular and energy distributions of the positive and negative fragment ions. The impulsive energy transfer to the liquid molecules and to internal energy of the scattered ions has been determined as a function of incoming energy and total scatter ing angle. The energy transfer in the ion/surface collision indicated scattering off the -CF3 groups of the liquid molecules. The dissociati on of the CF3+ ions was due to a single impulsive collision with these groups. The parent ion was observed as well as CF2+, CF+, and C+ ions . The degree of dissociation depends only on the total scattering angl e and the incoming energy, as in gas phase scattering. Remarkably, neg atively charged F(-)fragment ions were also observed. These were forme d in a process referred to as collisionally-induced ''ion-pair'' forma tion from neutrals leaving the surface. The important parameter which determined the internal energy uptake of the scattered ions in the col lision was the translational energy loss Delta E the parent ion suffer ed. Finally, a comparison has been made between scattering from a liqu id perfluorinated polyether surface and a metal Ag(111) surface. (C) 1 997 American Institute of Physics.