Born May 9, 1927, in Bochum. German physical chemist (Federal Republic of Germany).

Eigen graduated from the University of Göttingen in 1951. He joined the staff of the Max Planck Institute of Physical Chemistry in 1953 and became chairman of the institute in 1964.

Eigen’s principal works are devoted to the development of methods for investigating the kinetics of chemical reactions. He proposed a class of methods known collectively as the relaxation method for studying extremely fast chemical reactions. The term is used to describe a method in which the chemical equilibrium of a system is disturbed and the rate at which the system returns to equilibrium is observed; the equilibrium is disturbed by sending a single energy pulse or periodic pulses through the system in order to affect such factors as temperature, pressure, and electric field. Using this method, Eigen and his colleagues studied, for example, the kinetics of reactions of hydrogen and hydroxyl ions in aqueous solutions with acid-base indicators. Another important study involved the kinetics of the association of carboxylic acids.

Together with R. Norrish and G. Porter, Eigen won a Nobel Prize in 1967.