The 1967 Nobel Prize: Fifty years later
"For their studies of extremely fast chemical reactions, effected by disturbing the equilibrium by means of very short pulses of energy." In 1967 these words accompanied the Prize, awarded for the understanding of chemical kinetics.
Chemical reactions chiefly rely on the formation of substances from reactants, but not all reactions are equal. While some can be measured with a rudimentary clock, others proceed at velocities which currently defy measurement with all but the most sophisticated technology.
Take for example the process of electron transfer, which typically proceeds on the femtosecond timescale, 10-15 s or one quadrillionth of a second. To put it into perspective, a femtosecond can be said to form the same part of a second as a second is to 31,688,764 years.
The story of flash photolysis began in the 1940’s when Professor Norrish and his then associate George Porter set out to study reaction kinetics by using a flash lamp. The idea was to have a system set up in an equilibrium, which is then disturbed by an external stimulus.
The process of flash lamp photolysis is as follows: a substance is placed next to the lamp, which provides the stimulus required to excite the substance into an activated form or for molecules to be broken up. It is then possible to study these molecules spectroscopically.
The now Lord Porter moved to Sheffield in 1955 where he remained until he moved to the Royal Institute in 1966. By the time George he moved to Sheffield, he expanded on the uses of flash photolysis demonstrating its uses in organic and biological chemistry. Refinements to the method were made over the years, most notably with the discovery of the laser meaning shorter pulses could be performed recording picosecond timescales.
The importance of their method cannot be understated, and was articulated perfectly by Nobel Prize presenter Prof. H. Olander:
Detailed knowledge of the behaviour of activated molecules was meagre and most unsatisfactory. Your Flash Photolysis method provides a powerful tool for the study of various states of molecules and the transfer of energy between them.
Prof. H. Olander
Nobel Prize presenter
Fifty years have passed since George Porter and Ronald Norrish developed flash photolysis. In this time their method has been used countless times to study kinetics and is still in use today. The advent of new improved technology may have lead to improvements in measurement speed and shorter timescale of study, but it still required the innovation and vision of the first pioneering researchers.
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