Percolation effects on the decay of admolecules

The effects of percolation on the energy transfer from an admolecule to a two-component granular composite substrate are investigated. The substrate material is a random mixture of a metal and an insulator nonabsorptive to the light. The luminescence decay rate of the admolecule near the composite surface is calculated by means of the effective-medium theory as a function of the volume fraction of the metallic granules. It is found that the decay rate is greatly enhanced around the dc conduction percolation threshold at low transition frequencies. For high frequencies, the decay rate peaks at a higher volume fraction of the metallic particles, indicating the existence of a surface-percolation threshold.