Recombination on fractal networks: Photon and electron emission following fracture of materials

We report measurements and analysis of fracture-induced photon and electron emissions from several polymeric and inorganic systems on time scales of 10⁻² to 10³ s following fracture. The dominant mechanism for postfracture emission involves the recombination of mobile free carriers (usually electrons) with immobile recombination centers. The emission decays were modeled as (pseudo)unimolecular and bimolecular recombination on fractal lattices as described by Zumofen, Blumen, and Klafter.¹ Although the decay kinetics shows a great deal of variability from material to material, this random walk description of the recombination process provides an excellent description of the emissions over long time scales. This analysis shows a strong correlation between the local structure at the fracture surface and the resulting decays.