Some observations on molecular complexes of carbon monoxide in argon and oxygen nutrices

Aggregates of CO were generated in Ar and O₂ matrices by several methods, including deposition of concentrated samples, warming experiments, and photolysis of H₂CO and H₂C₂O₂. The IR absorption frequencies of the CO species were measured by an FTIR spectrometer. In solid Ar, the CO monomer was seen to absorb at 2138.5 cm^?1 and (CO)₂ at 2136.6 cm^t-1. In systems containing only CO and Ar, no distinct peak was observed at 2140 cm^?1 in contrast to previously reported results. The difference may be due to effects of H₂O on CO frequencies and intensities. In solid O₂, the CO monomer absorbed at 2136.6 cm^?1, but it was not possible to assign a structure to (CO)₂ because of a more complicated absorption spectrum than in solid Ar. The spectral data suggest that the CO dimer absorbing at 2136.6 cm^?1 in solid Ar may have a side-by-side antiparallel geometric structure.