CHEMICAL STUDIES ON SILVER CLUSTER NUCLEA TION ON (100)-AGBR SURFACES

We have studied the first steps of a photolytic cluster nucleation on a (100)-AgBr-surface using quantum chemical model calculations. Accord ing to our calculations the negative kink is the most favourable site for the alternating adsorption of an interstitial silver ion and trapp ing of a photo-electron. The dependence of the electron affinity on th e cluster size (see Fig. 2) explains why nucleation does not start on many sites simultaneously. According to our results sensitization can not be achieved by single silver sulfide molecules (with sulfur substi tuting a bromide ion). A minimum size of the Ag2S clusters is probably necessary to form sensitivity centers.