1. This method has been used for example to observe the decay of metastable states of helium-like argon; see Schmieder, R.W., Marrus, R.: Phys. Rev. Letters25, 1245 (1970)
2. For a review on the plasma focus see Mather, J. W., in: Methods in Experimental Physics, Vol. 9, Part B, ed. R. Lovberg and H.R. Griem. New York: Academic Press 1971
3. Lie, T.N., Elton, R.C.: Phys. Rev. A3, 865 (1971)
4. Fraenkel, B.S., Schwob, J.L.: Phys. Letters40A, 81, 83 (1972)
5. Wood, R.W.: Phys. Rev. V, 1 (1897)