ELECTRONIC-STRUCTURE OF ADSORBED ALKALI ATOMS FOR COMPARISON WITH UPS DATA

We have generalised our earlier work calculating the induced density of states in alkali chemisorption to include the valence np level in addition to the s level. This allows the theory to take account of the possibility of sp hybridization. Hybridization is said to be weak is the sp level separation ΔEsP exceeds twice the width of the s or pz resonance. In the converse case hybridization is strong and the induced density of states no longer reflects distinguishable s and pz resonances. We argue that ΔEsP for the chemisorbed alkali exceeds considerably that for the free alkali atom. In the case of Na on rs = 2 jellium (considered typical of the smaller alkali on rs = 2-3 substrates) hybridization is strong for the atomic value of ΔEsp but weak when a somewhat larger value is taken, making the conclusions a little indefinite. For Cs on Cu(111), we find a clear situation of weak hybridization with the atomic ΔEsP and a fortiori with a more realistic value. There should thus be a well defined 6s resonance in this system. Our estimate of the width of the 6s resonance is in good agreement with photoemission data. © 1979.