Millimeter/submillimeter velocity modulation spectroscopy of FeO+ (X 6Σ+): Characterizing metal oxide cations

The pure rotational spectrum of FeO+ (X 6Σ+) has been recorded using millimeter/submillimeter velocity modulation techniques, the first high-resolution measurement of a metal oxide cation. FeO+ was created in an AC discharge from Fe(CO)5 and N2O. Nine rotational transitions were recorded in the range 299–544 GHz, each consisting of six fine-structure components. The data were analyzed with a case (b) Hamiltonian, and rotational and spin parameters determined. The spin–spin constant suggests a low-lying 4Σ− excited state. The bond length established for FeO+, r0 = 1.641 Å, is slightly longer than that of FeO, consistent with a covalent bonding scheme.