The vibrational spectra of molecular ions isolated in solid neon. II. O+4 and O−4

When a relatively concentrated Ne:O2 sample is codeposited at ∼5 K with a beam of excited neon atoms, prominent infrared absorptions appear which are assigned to O+4 and O−4. Absorptions of O3 and O−3 are also present, and their product distributions in isotopic substitution experiments indicate that O-atom production and reaction is a minor channel in this experimental system. Detailed isotopic substitution experiments require that both O+4 and O−4 possess two equivalent O2 units. Analysis of the isotopic shifts strongly favors a planar trans configuration (C2h) for both molecules. Several combination bands of O+4 are observed, and give evidence regarding the position of ν1(ag), which is infrared inactive, and regarding perturbations by combinations of low-frequency fundamentals. The mechanism of photodestruction of the ions in this system is also considered.