Manfred Eigen (1927- present) was awarded half of the 1967 Nobel Prize in Chemistry for his work on extremely rapid chemical reactions. He invented â€œrelaxation techniquesâ€ to study these reactions. The techniques involve the application of bursts of energy to a solution that briefly destroys its equilibrium. Eigen studied what happened to the solution in the extremely brief interval between the destruction of the equilibrium and the establishment of a new equilibrium, using absorption spectroscopy â€“ a technique for determining the structure of a substance by measuring the intensity of radiation it absorbs. Among specific topics he investigated were the rate of hydrogen ion formation through water dissociation, diffusion-controlled protolytic reactions (in which an acid and base are both spreading and reacting by exchanging protons and producing another acid and base), and the kinetics of keto-enol tautomerism (chemical equilibrium between a ketone or an aldehyde and an enol).