The radiative rate constant (k(r)) and the lifetime of singlet oxygen were measured in 17 new solvents with low and high ionization potentials (IP) using an IR laser fluorimeter. Analysis of the values of k(r) = 0.1-3.1 s(-1) in 63 solvents shows that the charge-transfer interaction is the main factor in removal of the prohibition on the radiative spin-forbidden transition (1)Delta(g) --> (3)Sigma(g)(-) oxygen and leads to an increase in the k(r) values in solvents with low ionization potentials. There is no correlation of k(r) with the energy of dispersion interactions in collision complex O-2((1)Delta(g))... solvent. The averaged contribution of the dispersion interactions in the k(r) dependence on the nature of solvent is estimated at 10%.