Laser-ablated manganese atoms react with oxygen in excess argon on condensation to form the neutral MnO and MnO2 oxide molecules as the major products. The MnO2 anions were produced via capture of ablated electrons by the neutral molecules. On annealing, the MnO4- anions were also formed and identified based on isotopic substitutions as well as density functional frequency calculations. Doping with CCl4 to serve as an electron trap gave the same neutral absorptions and virtually eliminated the anion absorptions, which strongly supports the anion identification. (C) 2002 Elsevier Science B.V. All rights reserved.