Chemiionization reactions of Mg, Ca, Sr and Ba with O₂(X³Σ_g^-), O₂(a¹Δ_g) and O(³P)

Abstract

The associative ionization reactions of Mg, Ca, Sr and Ba with O₂(X³Σ_g^-), O₂(a¹Δ_g) and O(³P) have been investigated with chemiion and chemielectron spectroscopy. The spectrometer used has been described, and the results obtained have been rationalized in terms of possible exothermic associative ionization reactions and the ground states of the oxides MO and MO₂ known from experimental and theoretical evidence. For magnesium, no associative ionization was observed under any conditions. For M=Ca, Sr and Ba reacted with O₂(X³Σ_g^-), the results obtained indicate that M₂O₂⁺ is a primary chemiion formed via an M+MO₂^* reaction. In the presence of O₂(a¹Δ_g) and O(³P), the chemiion and chemielectron intensities were greatly reduced. An explanation, based on known neutral reactions for the three metals, is proposed. The main chemiion observed in the presence of discharged oxygen is M₂O⁺ arising from the reaction sequence The implications of these results for atmospheric chemistry are discussed.

References

1. J. M. C. Plane, Int. Rev. Phys. Chem., 1991, 10, 55.
2. D. W. Hughes, Space Sci. Rev., 1992, 61, 275.
3. C. F. Nien, B. Rajasekhar and J. M. C. Plane, J. Phys. Chem., 1993, 97, 6449.
4. C. P. Granier, J. P. Jegou and G. Megie, J. Geophys. Res., 1989, 94, 9917.
5. W. J. McNeil, S. T. Lai and E. Murad, Adv. Space Res., 1997, 19, 627.
6. G. R. Swenson, S. B. Mende, R. E. Meyerott and R. L. Rairden, Geophys. Res. Lett., 1991, 18, 401.
7. S. T. Lai, E. Murad and W. J. McNeil, J. Geophys. Res., 1992, 97, 4099.
8. S. T. Lai, W. F. Denig, E. Murad and W. J. McNeil, Planetary Space Sci., 1988, 36, 841.
9. S. T. Lai, W. J. McNeil and E. Murad, J. Geophys. Res., 1988, 93, 5871.
10. O. J. Orient, K. E. Martus, A. Chutjian and E. Murad, Phys. Rev. A, 1992, 45, 2998.
11. A. Fontijn, Pure Appl. Chem., 1974, 39, 287.
12. N. Jonathan, A. Morris, M. Okuda and D. J. Smith, J. Chem. Phys., 1971, 55, 3046.
13. (a) J. M. Dyke, A. M. Shaw and T. G. Wright, J. Phys. Chem., 1994, 98, 6327; (b) J. M. Dyke, A. M. Shaw and T. G. Wright, J. Phys. Chem., 1995, 99, 14207.
14. C. W. Bauschlicher, H. Partridge, M. Sodupe and S. R. Langhoff, J. Phys. Chem., 1992, 96, 9257.
15. D. K. Bulgin, J. M. Dyke, N. Jonathan, E. Lee and A. Morris, J. Electron. Spectrosc. Relat. Phenom., 1977, 12, 67.
16. D. A. Dahl, J. E. Delmore and A. D. Appelhaus, Rev. Sci. Instrum., 1990, 61, 607.
17. D. A. Dahl and J. E. Delmore, A. Simion PC/AT User's Manual Version 2.0, Idaho National Engineering Laboratory, EG&G Idaho Inc., 1986.
18. J. Lawton and F. J. Weinberg, Proc. R. Soc. London, Ser. A, 1963, 227, 469.
19. M. P. Gardner, C. Vinkier and K. D. Bayes, Chem. Phys. Lett., 1975, 31, 318.
20. T. A. Cool, Appl. Opt., 1984, 23, 1558.
21. J. M. Dyke, A. M. Shaw and T. G. Wright, in Gas-Phase Metal Reactions, ed. A. Fontijn, Elsevier, Amsterdam, 1992, p. 467.
22. W. J. van der Meer, P. van der Meulen, M. Volmer and C. A. De Lange, Chem. Phys., 1988, 126, 385.
23. A. M. Shaw, J. M. Dyke, V. Zengin and S. Suzer, Chem. Phys., 1994, 179, 455.
24. M. C. R. Cockett, L. Nyulászi, T. Veszprémi, T. G. Wright and J. M. Dyke, J. Electron. Spectrosc., Relat. Phenom., 1991, 57, 373.
25. (a) R. W. Field, J. Chem. Phys., 1974, 60, 2400; (b) M. Farber and R. D. Srivastava, High. Temp. Sci., 1975, 7, 74.
26. J. M. Dyke, M. Feher, B. W. J. Gravenor and A. Morris, J. Phys. Chem., 1987, 91, 4476.
27. K. P. Huber and G. Herzberg, Molecular Spectra and Molecular Structure, Vol. IV , Constants of Diatomic Molecules, Van Nostrand, New York, 1979.
28. L. Thomas, J. Atmos. Terr. Phys., 1976, 38, 61.
29. R. P. Wayne, Chemistry of Atmospheres, Clarendon Press, Oxford, 2nd edn., 1991.