Ronald Norrish shared half the Nobel prize in chemistry with George Porter "for their studies of extremely fast chemical reactions, effected by disturbing the equilibrium by means of very short pulses of energy.” The other half was awarded to Manfred Eigen. Ronald Norrish describes photochemistry and photochemical processes in his Nobel lecture. In a photochemical reaction, for example, a molecule might absorb light at specific frequencies that provides enough energy for the molecule to dissociate (break apart). In studying these processes, Norrish and Porter decided to use very intense short flashes of a broad spectrum of light causing dissociation. They then applied a time-delayed secondary flash and observed the absorption spectrum of the free radicals and the recombination process. Using intense short pulses of light, Norrish and Porter also studied chemical kinetics, determining rates of fast reactions.