1. An account of these and related matters has been given by A. Cox and T.J. Kemp in Introductory Photochemistry, McGraw- Hill, London, 1970.
2. Th Förster, Disc. Faraday Soc. 27, 7 (1959).
3. R. F. Cozzens and R.B. Fox, J. Chem. Phys. 50, 1532 (1969).
4. R.B. Fox and R.F. Cozzens, Macromolecules 2, l8l (1969).
5. R.B. Fox, T.R. Price and R.F. Cozzens, J. Amer. Chem. Soc. 54, 79 (1971).