A study of the chemiionization reactions of Ca, Sr and Ba with O2(X 3Σ-g)

Abstract

Chemielectron and chemiion spectra resulting from the reactions of effusive beams of Ca, and Sr and Ba (in their ground 1S states) with ground state molecular oxygen O2(X 3Σ- g) have been recorded using electron spectroscopy and mass spectrometry. The chemielectron spectra are similar for all three reactions exhibiting a strong near-zero energy band and another band at higher electron energies. The chemiion spectra show O+ 2, M+ and M2O+ 2 as the major ions. The total ion current as well as the individual ion intensities, have been recorded as a function of the extraction potential on the reaction cell. The results obtained indicate that the metal oxide dimer ion is the primary chemiion, formed via an associative ionization reaction of a metal atom with a long-lived metal superoxide intermediate MO2. A two state potential energy curve model is proposed for the M+MO2 reaction to explain the shape of the experimental electron distribution. © 1994.