In aqueous solution, Na polystyrenesulfonate (NaPSS) increases the local concentration of ionic dyes Acridine Orange and Pyronine around macroions and enhances excimer formation of Acridine Orange and the efficiency of energy transfer from excited Acridine Orange to Pyronine ground state. In the presence of 10-4 mol dm-3 NaPSS the excimer formation rate constant of Acridine Orange is enhanced by 102 times and the dissociation rate constant of the excimer is decreased 10 times, indicating that excimer, at least in part, is generated from preformed complexes i.e. configurations in which 2 Acridine Orange mols. are in close contact at the instant of absorption. NaCl retards excimer formation of Acridine Orange.

Key words: SODIUM COMPOUNDS, ACRIDINE P, XANTHENE P, REACTIVITY, POLYSTYRENE, SULFONATE, DYES, EXCITED STATE, QUENCHING EFFECTS, REACTION RATE CONSTANT