S. Pulm et al., IODINE ADSORPTION ON CLEAN AND CESIATED W(110) STUDIED WITH UPS AND METASTABLE IMPACT ELECTRON-SPECTROSCOPY (MIES), Surface science, 325(1-2), 1995, pp. 75-84
Photoemission spectra (UPS with HeI) and metastable impact electron sp
ectroscopy (MIES with He(1s2s)) are reported for the adsorption of io
dine 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 t
he iodine adsorbate. For iodine in a strong external field, such as fo
r adsorption on clean metals, the photoemission spectra reflect the St
ark splitting of the (5p) orbital while the MIES spectra are due to th
e Auger capture process. When adsorbed near to cesium iodine feels a c
omparatively weak external field and the emission spectra both for UPS
and MIES (due to the Anger deexcitation process) reflect the I(5p) fi
nestructure splitting in the final state after the emission process.