Self-ordering in diffusion-controlled reactions: Exciton fusion experiments and simulations on naphthalene powder, percolation clusters, and impregnated porous silica

Reactive self-ordering is demonstrated for the elementary reaction $A+A\to \mathrm{product}$ in low-dimensional media, via both simulations and experiments. In one dimension, an effective spacing of excitations is created (order of 10 lattice units). The experimental verification involves excitation-time modulation, a new technique for microstructural studies. Naphthalene-impregnated porous glass (Vycor), naphthalene isotopic alloys, and naphthalene crystalline powder all show the self-ordering effect for triplet exciton annihilation.