ANGLE-RESOLVED DIET OF NEGATIVE-IONS FROM HALOGENATED MOLECULES ON RU(0001)

We present data on the electron stimulated desorption(ESD) of negative ions from PF3 and CCl4 adsorbed on Ru(0001) at 100 K. We use a two-di mensional digital ESDIAD detector with time-of-flight capability which allows mass and angle resolved ion detection. We find F- and F-2 to d esorb from PF3, yielding hexagonal ESDIAD patterns, and Cl- and Cl-2(- ) from CCl4, desorbing in a broad normal emission. The ratio of F-2(-) to F- and of Cl-2(-) to Cl- is more than a factor 10 higher than in e lectron induced gas phase dissociation. We compare the negative ion yi elds to those of positive ions.