Abstract
Effects of diffusion on energy transfer between molecules are considered by using two methods. One is the scattering length method, and the other is the Padé approximant with the diffusion constant as the expansion parameter. From these methods we obtain the decay function of the emission by excited molecules in a closed form of time t. The decay constant is expressed as a function of diffusion constant and is compared with the experimental results obtained by Tomura and Ishiguro.