Photoemission spectra (UPS with HeI) and metastable impact electron spectroscopy (MIES with He∗(1s2s)) are reported for the adsorption of iodine alone, the coadsorption of iodine and cesium, and the adsorption of CsI on W(110) at room temperature. It is demonstrated that the I(5p) ionization is sensitively dependent on the chemical environment of the iodine adsorbate. For iodine in a strong external field, such as for adsorption on clean metals, the photoemission spectra reflect the Stark splitting of the (5p) orbital while the MIES spectra are due to the Auger capture process. When adsorbed near to cesium iodine feels a comparatively weak external field and the emission spectra both for UPS and MIES (due to the Auger deexcitation process) reflect the I(5p) finestructure splitting in the final state after the emission process.