Effect of solvent on the radiative decay of singlet molecular oxygen (a¹Δ_g)

Relative rate constants for O₂(a¹Δ_g) radiative deactivation (k_r) have been determined in 19 solvents. The data are consistent with earlier results that were obtained by using a different technique [Scurlock, R. D.; Ogilby, P. R. J. Phys. Chem. 1987, 91, 4599]. Of particular interest are the data in CS₂, which heretofore had yet to be corroborated. Current results indicate that k_r for CS₂ is indeed ∼2 times larger than k_r for benzene. A compilation of these results, along with those of other investigators, is provided. Average values of k_r derived from this compilation correlate well with both the solvent refractive index and solvent polarizability. The data correlate less well with the solvent ionization potential. Possible mechanisms consistent with these data are discussed.