Momentum-resolved inverse photoemission study of nickel surfaces

Abstract

Momentum-resolved inverse photoemission spectra from Ni(001), Ni(110), and Ni(111) have been measured. The results are presented in terms of final-state dispersions E(k${\to }_{\parallel }$) and compared to theoretical predictions on the basis of the bulk direct-transition model. Good agreement is found for the energies of bulk interband transitions. In addition to bulk direct transitions a wealth of surface bands has been identified. These include crystal-induced surface states as well as surface bands which arise from the long-range nature of the image-potential barrier. Effective masses of the image-potential surface bands as large as 1.7 for Ni(110) emphasize the importance of surface corrugation.