Line Broadening in NMR and ESR Spectra

All spectroscopic lines have a natural line width, and this can be of great use to the kineticist. This natural line width is determined by the lifetime of the excited state of the molecule. If this is short the line width is broad, while longer lifetimes give more sharply defined lines. If reaction occurs, this can alter the lifetime of the excited state and so change the natural line width of the transition. A detailed spectroscopic analysis gives relations between the width of the line, the lifetime of the reacting species and the rate constant for the reaction. This has proved a very important tool, especially for reactions in solution such as proton transfers and acid/base ionization processes. 

Laidler K.J. and Meiser J.H., Physical Chemistry, 3rd edn, Houghton Mifflin, New York, 1999. 

Alberty R.A. and Silbey R.J., Physical Chemistry, 2nd edn, Wiley, New York, 1996. Logan S.R., Fundamentals of Chemical Kinetics, Addison-Wesley, Reading, MA, 1996. 

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