PREDICTION OF A AG MULTIPOLE SURFACE-PLASMON

It is argued that Ag should exhibit a multipole surface plasmon near o mega(m) approximate to 0.8 omega(p) approximate to 7 eV (omega(p) appr oximate to 9 eV is the s-electron bulk plasma frequency) since the den sity profile at the surface has predominantly s-electron character and since the multipole mode is much less affected by s-d screening than the monopole surface plasmon. Calculations of nonlocal optical spectra based on the s-d polarization model and the time-dependent density fu nctional approach support this picture. [S0163-1829(98)01407-6] .