Photochemistry is concerned with the study of the chemical effects induced by the absorption of light (typically 200 nm-800 nm) whereas Radiation Chemistry concerns the effects induced by ionising radiations(typically X- and y-rays, electrons, protons, a-particles, etc.). Major sources of light are discharge lamps (e.g. various pressure Hg arcs) and lasers while sources of radiation can arise with the continuous emission from isotopes (e.g. 60Co) or the continuous or pulsed radiation from machines such as a Van de Graaff accelerator, the Febetron, or, more importantly, a linear-electron accelerator. The absorption of both high-energy radiation and light, can lead to similar short-lived species such as electronically excited states (singlet or triplet) and, particularly in the case of radiation chemistry, to ions, free radicals and the solvated electron. The study of these short-lived intermediates requires the use of a suitable fast-reaction technique. In photochemistry the technique of choice is flash photolysis while the complementary technique of radiation chemistry is pulse radiolysis. The time resolution of both techniques continues to shorten with new technology and pico-second (and in a few cases even faster) pulses are almost routine for studying ultra-fast processes (West, 1986). However, much of the data obtained in biological work have used nano-second pulses and this lecture will mainly concern such studies. Nevertheless, major advances in, for example, our understanding of photosynthesis, vision and haemoglobin binding have depended on pico-second and femto-second studies.
KeywordsTriplet State Flash Photolysis Pulse Radiolysis Radiation Chemistry Laser Flash Photolysis
Unable to display preview. Download preview PDF.
Typical General References
- Bensasson, R.V., Land, E.J. and Truscott, T.G., 1983, Flash Photolysis and Pulse Radiolysis:Contributions to the Chemistry of Biology and Medicine, (Pergamon Press).Google Scholar
- Butler, J., Hoey, B.M. and Swallow, A.J., 1986, Radiation Chemistry. R.S.C. Ann. Report C, 129–175.Google Scholar
- Dorfman, L.M. and Sauer Jr., M.C., 1986, Pulse Radiolysis. Chapter IX from Investigation of Rates and Mechanisms of Reactions Part II, Edited by C.F. Bernasconi, 4th Ed. (J. Wiley) pp.493–546.Google Scholar
- Farhataziz and Rodgers, M.A.J., 1987, Radiation Chemistry (VCH Publishers)Google Scholar
- Hughes, G., 1973, Radiation Chemistry (OUP).Google Scholar
- Swallow, A.J., 1973, Radiation Chemistry (Longman).Google Scholar
- West, M.A., 1986, Flash and Laser Photolysis. Chapter VIII from Investigation of Rates and Mechanisms of Reactions Part II, Edited by C.F. Bernasconi, 4th Ed. (J. Wiley), pp. 391–491.Google Scholar
- Chedekel, M.R., Land, E.J., Thompson, A. and Truscott, T.G., 1984, Early steps in the free radical polymerisation of 3,4-dihydroxyphenylalanine (dopa) into melanin. J. Chem. Soc., Chem. Comm., 1170–1172.Google Scholar