1. Early recognition of the potential of atomic vapor laser isotope separation is generally attributed to Ambartzumian and Letokhov [Ambartzumian 1972] following their experimental work on selective photoionization of rubidium [Ambartzumian, 1971], and Levy and James [Levy, 1973]R.V. Ambartzumian, V.S. Letokhov: Appi. Opt, 11, 354 (1972)
2. R.V. Ambartzumian, V.N. Kalinin, V.S. Letokhov: JETP Lett. 13, 217 (1971)
3. R.1-1. Levy, G.S. James: Method and Apparatus for the Separation of Isotopes, U.S. Patent 3,772, 519 (1973)
4. For a more extensive discussion of resonant multistep photo-ionization, see L.J. Radziemski, R.W. Solarz, J.A. Paisner (eds.) Laser Spectroscopy and Its Applications ( Dekker, New York 1987 ), pp. 175
5. V.S. Letokhov: Laser Photoionization Spectroscopy (Academic. Orlando, Florida 1987 )