Quenching of 1,2-benzanthracene (BA) by CBr4 was studied by frequency-domain fluorometry. The frequency response of the BA emission could not be fit using the Smoluchowski decay law for transient effects in quenching, exp(-t/τ-2bt 1 2). However, the data were consistent with the expression for the radiation boundary conditions. We believe these are the first reported data which support the "radiation boundary condition" model for collisional quenching. Our ability to detect the inadequacy of the t 1 2 model indicates that the frequency-domain method can yield considerable detail about diffusive processes in solution.