Why can coupled chemical reactions produce more than one relaxation time?

In the study of chemical reactions, a system typically exhibits a specific relaxation time—the duration required for the system to re-equilibrate following a disturbance. However, when multiple chemical reactions are coupled, the system's response becomes more complex.12

In such cases, a spectrum of relaxation times may be observed rather than a single value. These measured relaxation times represent the normal modes of the coupled system. Essentially, because the reactions are interdependent, the individual relaxation processes interact, and the overall system's return to equilibrium is characterized by these distinct normal modes, each corresponding to a different relaxation time. By analyzing these multiple times, researchers can determine the relaxation times for the individual processes involved in the mechanism.1