Molecular dynamics tests of the Smoluchowski–Collins–Kimball model for fluorescence quenching of spherical molecules

Abstract

We test the Smoluchowski–Collins–Kimball (SCK) model of fluorescence quenching reaction in liquids. Our attention is focused on the description of diffusion controlled processes and we use the simplest microscopic model of binary de-excitation which occurs instantaneously. Molecular dynamics simulations have been performed for a wide range of densities and for various potentials of interparticle interactions. The large number of particles used (typically N = 681 472) allowed us to obtain quantitative results. The simulations show that at very short times the SCK model completely fails, especially if the distribution function of the reagents is not included in the model. Even if the short time data are excluded the diffusion constant obtained by fitting the simulation data with the SCK model may still be burdened with a 25% error when the distribution function is not taken into account. The error can be reduced to 10% level if this function is included in the model.