Interesting online CONFCHEM discussion going on right now on the ChemWiki and
greater STEMWiki Hyperlibary project. Come join the discussion.

ChemWiki: The Dynamic Chemistry Hypertext > Physical Chemistry > Kinetics > Reaction Rates > Experimental Determination of Kinetics > Relaxation Methods > Flash Photolysis

Flash Photolysis

Table of Contents

In 1967 the Nobel Prize in Chemistry was awarded to Manfred Eigen, Ronald George, George Porter and Wreyford Norrish for their co-discovery of Flash Photolysis in 1949. Flash Photolysis is used extensively to study reactions that happen extremely quickly, even down to the femtosecond depending on the laser that is used. The technique was born out of cameras developed during and shortly after WWII, which were used to take pictures of fast moving planes, rockets, and missiles. Since then the technology of lasers and optics has progressed allowing faster and faster reactions to be studied.

Flash Photolysis is often used to study reactions that are light dependent such as photosynthesis and reactions in the cones on the retina of the our eye, but the meathod can also be applied to other reactions. The light in the form of a laser excites a molecule into a reactive state, usually in the form of a free radical. From there it is possible to measure the reaction spectroscopically, using the exitory flash as a light source to measure absorbance. The laser pulse must be aproximatly half the length of the reaction, and of sufficient energy to induce the reaction to take place. Further the flash must cover the spectrum of frequencies which are being studied because not only is the flash producing intermediates of the reaction that are usually not observed, it is also producing the source for spectroscopic analysis. Intermediates of most reactions are rarely observed, this techniques isolates even low concentrations of otherwise unobservable portions of reactions allowing research into synthetic, biochemical, and photo-sensitive reactions.


  1. Porter,G. Flash Photolysis and Spectroscopy. A New Method for the Study of Free Radical Reactions. Proceedings of the Royal Society of London. Series A, Mathematical and Physical Sciences, Vol. 200, No. 1061. (Jan. 6, 1950), pp. 284-300.|external link:
  2. 1967 Nobel Prize in Chemistry|external link:


  • Aaron Whiteley

You must to post a comment.
Last modified
09:28, 2 Oct 2013



(not set)
(not set)

Creative Commons License Unless otherwise noted, content in the UC Davis ChemWiki is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 3.0 United States License. Permissions beyond the scope of this license may be available at Questions and concerns can be directed toward Prof. Delmar Larsen (, Founder and Director. Terms of Use