Using a laser double ablation reactor built on the basis of a tandem time-of-flight mass spectrometer (TOF MS), we studied the reaction of clusters produced by laser ablation of silver (potassium) bromide and silver sulfur powder mixture. The results showed that reactions took place and that Ag/S/Br ternary cluster anions were produced. The formation of Ag/S/Br clusters is considered to occur by the addition of bromine atom to the silver sulfide cluster anions. The results provide grounds for the argument we proposed that silver sulfide cluster anions can act as positive hole traps during the exposure of photosensitive silver bromide microcrystals.