Abstract

The photodissociation of the strongly solvated radical O₃^- (generating O₂ and O^-) has been studied in aqueous solution by femtosecond pump-probe spectroscopy for the first time. This study of O₃^- represents the first femtosecond pump-probe study of the photodissociation and geminate recombination of a triatomic radical anion in solution. I₃^-, a non-radical, is the only other charged triatomic in solution whose photodissociation has been studied with comparable time- resolution.¹ From a solution dynamics standpoint there are many features of O₃^- which make it an interesting radical to examine. O₃^- has highly concentrated charges (small atomic radii) leading to extraordinarily large electrostatic solute/solvent interactions. O₃^- has two high-frequency vibrational fundamentals (1058 cm^-1, 880 cm^-1), thus requiring a quantum mechanical description of the relaxation process. Finally, O₃^- has a much lower dissociation energy in water (D_e = 0.34 eV) than the gas phase (D_e =1.7 eV), further emphasizing the especially strong solute/solvent coupling in this system.

© 1996 Optical Society of America