1. Shimoni, Y., Wilson, A.D.: Chem. Phys. (Netherlands),11, 289 (1975)
2. Roueff, E.: J. Phys. B8, L429 (1975)
3. Gayet, R., Brouillaud, B.: private communication; to be published
4. Roueff, E.: private communication
5. Gordeyev, E.P., Nikitin, E.E., Ovchinnikova, M.Ya.: Can. J. Phys.47, 1819 (1969)