Reaction of laser-ablated Fe atoms with oxygen molecules in a condensing argon stream produced FeO, FeO2, FeO3, FeO4, Fe2O, Fe2O2, and Fe2O4 molecules, which are identified from oxygen isotopic shifts and multiplets in matrix infrared spectra. The Fe + O2 reaction gives symmetrical bent, symmetrical cyclic, and asymmetrical bent FeO2 isomeric products with triplet, triplet, and quartet isotopic absorptions, respectively, using statistically mixed 16,18O2 as the reagent. The major reaction product symmetrical bent OFeO iron dioxide molecule (150 ± 10°) is characterized by stretching fundamentals at 945.8 and 797.1 cm-1, and the asymmetric bent FeOO form exhibits a 1204.5 cm-1 absorption. The cyclic isomer Fe(O2) produced spontaneously during annealing in solid argon absorbs at 956.0 cm-1. Oxygen and iron isotopic absorptions show that FeOFe is a symmetrical bent (140 ± 10°) molecule. Rhombic Fe2O2 absorbs at 517.4 cm-1. Evidence is presented for isomers of FeO3, FeO4, and Fe2O4. Density functional theory was used to calculate energies, structures, and frequencies for product molecules to support their identification.

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Reactions of laser-ablated Cr atoms with O2 gave a very strong, sharp 965.4 cm−1 band and weak, sharp 1869.7, 984.3, 914.4, 846.3, 716.2, and 643.1 cm−1 bands. The 1869.7, 965.4, and 914.4 cm−1 bands track together on annealing, show 52Cr, 53Cr, 54Cr isotopic splittings appropriate for a single Cr atom and triplets with statistical 16,18O2 for two equivalent O atoms, and are assigned to the ν1+ν3, ν3 and ν1 modes of the bent (128°±4°) chromium dioxide OCrO molecule. The 984.3 cm−1 band shows chromium isotopic splittings for two Cr atoms and 16,18O2 components for two O atoms, and is attributed to the bent CrOCrO molecule. The weak 846.3 cm−1 band exhibits proper oxygen isotopic behavior for CrO and is redshifted 39 cm−1 from the gas-phase value, the maximum shift observed for a first row transition metal monoxide. The sharp 716.2 and 643.1 cm−1 bands track together; the former reveals Cr isotopic splittings for two Cr atoms and the latter 16,18O2 splittings for two sets of dioxygen subunits; the branched-puckered-ring dimer O(Cr2O2)O is identified. Annealing produces new bands due to CrOO, CrO3, Cr(OO)2 and the ring dimers (Cr2O2) and (Cr2O2)O, which are identified from isotopic shifts and splitting patterns.

Laser-ablated iron atoms have been reacted with CO molecules during condensation in excess argon. The FeCO molecule is observed at 1922.0 cm−1 in solid argon based on concentration studies, isotopic shifts, and density functional theory frequency calculations; the argon matrix redshifts this band 27.0 cm−1 (1.4%) from the high-resolution gas phase measurement. Absorptions at 1879.2 and 1984.8 cm−1 are assigned from isotopic substitution and density functional theory frequency calculations to the antisymmetric and symmetric vibrations of a bent Fe(CO)2 molecule in the matrix. The Fe(CO)x (x=3,4,5) molecules are also observed on annealing in agreement with earlier matrix work. Iron carbonyl ions were also produced and trapped: photosensitive absorptions at 1770.3, 1721.9, 1815.0, 1786.5, and 1853.5 cm−1 are assigned to FeCO−, Fe(CO)2−, Fe(CO)3−, and Fe(CO)4−, respectively, and a weak photosensitive 2081.5 cm−1 band is assigned to FeCO+. Polynuclear metal carbonyls were also formed on annealing; based on different CO concentration and laser power experiments and isotopic substitution, an 1897.7 cm−1 absorption is assigned to Fe2CO and a 1948.5 cm−1 band to Fe3CO.