Infrared spectra of zinc and cadmium dioxide anions in solid neon

Zinc and cadmium dioxide anions are produced via electron capture of the corresponding neutral molecules during condensation of laser-ablated zinc and cadmium atoms with O2 in excess neon at 4 K. Photosensitive infrared absorptions at 624.1 and 483.6 cm−1 are assigned to the antisymmetric stretching vibrations (ν3) of the linear ZnO 2 - and CdO 2 - anions on the basis of isotopic shifts and splittings as well as density functional calculations. The predicted quite low ν3/ν1 ratios for both anions with 2Πg ground state are similar with the valence isoelectronic CO 2 + and BO2 molecules.