The associative ionization reactions of Mg, Ca, Sr and Ba with O2(X 3Σg-), O2(a 1Δg) 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(X 3Σg-), the results obtained indicate that M2O2+ is a primary chemiion formed via an M + MO*2 reaction. In the presence of O2(a 1Δg) 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 M + O → MO** MO** + X → MO* MO* + M → M2O+ + e- The implications of these results for atmospheric chemistry are discussed.
|Number of pages||6|
|Journal||Journal of the Chemical Society - Faraday Transactions|
|Publication status||Published - Aug 21 1997|
ASJC Scopus subject areas
- Physical and Theoretical Chemistry