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

Reactions of laser-ablated Cr atoms with ${\mathrm{O}}_{\mathrm{2}}$ gave a very strong, sharp $\text{965.4\hspace{0.17em}}{\mathrm{cm}}^{\mathrm{-1}}$ band and weak, sharp 1869.7, 984.3, 914.4, 846.3, 716.2, and $\text{643.1\hspace{0.17em}}{\mathrm{cm}}^{\mathrm{-1}}$ bands. The 1869.7, 965.4, and $\text{914.4\hspace{0.17em}}{\mathrm{cm}}^{\mathrm{-1}}$ bands track together on annealing, show ${}^{52}\mathrm{Cr},$ ${}^{53}\mathrm{Cr},$ ${}^{54}\mathrm{Cr}$ isotopic splittings appropriate for a single Cr atom and triplets with statistical ${}^{\text{16,18}}{\mathrm{O}}_{\mathrm{2}}$ for two equivalent O atoms, and are assigned to the ${\nu }_1{\mathrm{+\nu }}_3,$ ${\nu }_3$ and ${\nu }_1$ modes of the bent (128°±4°) chromium dioxide OCrO molecule. The $\text{984.3\hspace{0.17em}}{\mathrm{cm}}^{\mathrm{-1}}$ band shows chromium isotopic splittings for two Cr atoms and ${}^{\text{16,18}}{\mathrm{O}}_{\mathrm{2}}$ components for two O atoms, and is attributed to the bent CrOCrO molecule. The weak $\text{846.3\hspace{0.17em}}{\mathrm{cm}}^{\mathrm{-1}}$ band exhibits proper oxygen isotopic behavior for CrO and is redshifted $\text{39\hspace{0.17em}}{\mathrm{cm}}^{\mathrm{-1}}$ from the gas-phase value, the maximum shift observed for a first row transition metal monoxide. The sharp 716.2 and $\text{643.1\hspace{0.17em}}{\mathrm{cm}}^{\mathrm{-1}}$ bands track together; the former reveals Cr isotopic splittings for two Cr atoms and the latter ${}^{\text{16,18}}{\mathrm{O}}_{\mathrm{2}}$ splittings for two sets of dioxygen subunits; the branched-puckered-ring dimer ${\mathrm{O(Cr}}_{\mathrm{2}}{\mathrm{O}}_{\mathrm{2}}\mathrm{)O}$ is identified. Annealing produces new bands due to CrOO, ${\mathrm{CrO}}_{\mathrm{3}},$ ${\mathrm{Cr(OO)}}_{\mathrm{2}}$ and the ring dimers ${\mathrm{(Cr}}_{\mathrm{2}}{\mathrm{O}}_{\mathrm{2}}\mathrm{)}$ and ${\mathrm{(Cr}}_{\mathrm{2}}{\mathrm{O}}_{\mathrm{2}}\mathrm{)O},$ which are identified from isotopic shifts and splitting patterns.