The adsorption and decomposition of Fe(CO)(5) on fcc and bcc iron films at 90 K were investigated using infrared reflection absorption spectroscopy (IRRAS). The fcc film was epitaxially grown on a Cu(1 0 0) crystal at room temperature, whereas the bcc film was deposited as polycrystalline by electron-beam evaporation onto a Si(1 1 1) wafer. The saturated adsorption of Fe(CO)(5) on the fcc Fe(1 0 0) surface yielded a dominant IRRAS band at 2060 cm(-1) due to the axial C-O stretch mode of Fe(CO)(5). Upon UV (254 nm) irradiation to the adsorbed layer, the 2060 cm(-1) band decreased in intensity and a new band appeared at 2072 cm(-1), indicating the photolytic decomposition of the adsorbed Fe(CO)(5). Fe(CO)(5) adsorption on the polycrystalline bcc surface gave rise to a single intense band at 2072 cm(-1) which was not changed in position by UV irradiation. We conclude from these results that the fcc(1 0 0) surface is inactive for the decomposition of Fe(CO)(5) in comparison to the polycrystalline bcc surface. (C) 2002 Elsevier Science B.V. All rights reserved.