In school you learn that reaction rates depend on concentration and temperature, but catching what happens in less than a millisecond is tricky. The laureates solved this by disturbing an equilibrium with a “temperature jump” or a brief flash of light, then watching the system relax back. They monitored concentration changes with spectroscopy and could thus see short-lived intermediates and decide which step in a mechanism is rate-limiting. The same methods measure how fast enzymes work or how ozone forms in the air, showing clear social value in medicine and environmental science.

Manfred Eigen developed microsecond temperature-jump techniques driven by acoustic shocks or electric discharges and provided the theoretical framework for extracting rate constants from relaxation curves. Ronald Norrish and George Porter pioneered flash photolysis, using xenon lamps and later lasers to obtain time-resolved UV–vis absorption spectra that visualized radical generation. Their experiments proved that proton transfer, electron transfer and the primary steps of photosynthesis can finish within micro- to nanoseconds. Combining temperature studies with Eyring plots allowed separate evaluation of activation enthalpy and entropy. Modern femtosecond laser spectroscopy and ultrafast X-ray science grew directly from this foundation.

Eigen applied nonlinear relaxation theory, extracting eigenvalues from multi-exponential decays to determine the reaction matrix of complex systems. Norrish and Porter engineered flash tubes delivering ~130 ns pulses, observed triplet–triplet quenching and biradical generation, and achieved ~10⁻³ OD sensitivity in the visible range. Their datasets provided early experimental support for the then untested Marcus electron-transfer model and the emerging concept of proton-coupled electron transfer. A combined T-jump/flash approach demonstrated pK shifts in buffered systems completing within microseconds, opening kinetic analysis of biomolecular conformational dynamics. Present-day 2D-IR and XFEL pump-probe studies simply extend the paradigm of “instantaneous equilibrium perturbation followed by time-resolved detection” into ever shorter domains.