Abstract
We show core-electron energy spectra determined by means of (soft) x-ray photoelectron spectroscopy and appearance potential spectroscopy to be closely related for 2p electrons in iron and nickel. An earlier comparison for the first transition-series elements had indicated a systematic difference between appearance-potential-spectroscopy data and tabulated values based on x-ray emission and hard-x-ray-excited x-ray photoelectron-spectroscopy data.