Resonant photoemission at the iron M-edge of Fe(CO)5

High resolution electron kinetic energy spectra of iron pentacarbonyl (Fe(CO)5) are studied in the photon energy range of 40–90 eV. The relative yield of photolines associated with the Fe 3d level shows a Fano line shape at photon energies of 61 eV. The increase in signal from the 3d level is indicative of resonant photoemission involving 3p-3d transitions at the M edge of iron. The signature of this resonance is also present in photolines typically attributed to be mostly CO in character. We use the modulation depth of the Fano resonances to reinterpret the photoelectron lines in the literature.