Percolation Effects on the Decay of Admolecules
Abstract
It is well known that, in a two-component particle composite material, the conductivity exhibits singular behavior near a percolation threshold, namely, a composition at which one of the constituents forms a connected path extending throughout the material. As an example, the effective conductivity of a composite material composed of metal and insulator particles varies as (q-q sub c) to the minus t power), near the metal percolation threshold q sub c , where q is the volume fraction of the metal and t is a characteristic exponent which remains to be determined. In addition to static properties, optical properties of the two--component composite material, both linear and nonlinear, have been extensively studied. In general, composite materials have optical properties very different from those of their constituents, especially in the vicinity of the percolation threshold. 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 non-absorptive 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 'bulk percolation' threshold.
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 01, 1991
- Accession Number
- ADA243149
Entities
People
- Dong Lin
- Thomas F. George
- Xiangchong Li
- Zhen-ya Li
Organizations
- Washington State University