Reactions of laser-ablated chromium atoms with dioxygen. Infrared spectra of CrO, OCrO, CrOO, CrO3, Cr(OO)2, Cr2O2, Cr2O3 and Cr2O4 in solid argon

Abstract

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.