Fractal chemical kinetics: Simulations and experiments

We relate the effective order X of the elementary binary reaction, A+A→ products, on a fractal, to the spectral dimension. For ds<2: X=1+2/ds. We regain the calsssical value (X=2) for the cubic lattice but get X=3 for the linear lattice. Supercomputer simulations (transient and steady state) and exciton fusion experiments are in quantitative agreement with the above. For percolating clusters X=2.5 and for the Sierpinski gasket X=2.45. Relevance to heterogeneous kinetics is discussed.