Influence of surface interband transitions on surface plasmon dispersion

We demonstrate that the qualitative difference of the Ag surfaces with respect to surface plasmon dispersion (nearly linear for Ag(001) and with strong isotropic quadratic term for Ag(111) and Ag(110)) is due to the presence on Ag(001) of interband transitions which nearly match the surface plasmon energy. A similar situation can be created for Ag(110) by K adsorption, obtaining a strong and abrupt decrease of the quadratic term, while the linear term is nearly unaffected, independently of the onset of the missing row reconstruction