Fano effect in the angle-integrated valence band photoemission of the noble metals Cu, Ag, and Au

Results of a combined experimental and theoretical investigation on the Fano-effect in the angle-integrated valence band photoemission of the noble metals are presented. In line with the fact that the Fano-effect is caused by the spin-orbit-coupling, the observed spin polarization of the photocurrent was found to be the more pronounced the higher the atomic number of the element investigated. The ratio of the normalized spin difference curves, however, agreed only for Cu and Ag with the ratio of the corresponding spin-orbit coupling strength parameters. The deviation from this expected behavior in the case of Au could be explained by the properties of individual $d\text{−}p$- and $d\text{−}f$-contributions to the total spin difference curves, that were found to be quite different for Au compared to Cu and Ag.

Figure 1

(Left) Spin and angle-integrated VB-XPS emission intensity $I$ of Cu, Ag, and Au for a photon energy of $600\mathrm{eV}$. (Right) Spin-difference $\Delta I_{+}=I_{+}^{\uparrow }-I_{+}^{\downarrow }$ of the photocurrent for excitation with circularly polarized radiation. Theory: full line; experiment: dots.

Figure 2

(Left) Spin and angle-integrated VB-XPS emission intensity $I$ of Au for different photon energies. (Right) Spin-difference $\Delta I_{+}=I_{+}^{\uparrow }-I_{+}^{\downarrow }$ of the photocurrent for excitation with circularly polarized radiation. Theory: full line; experiment: dots.

Figure 3

Decomposition of the theoretical photoemission intensity $I$ of Au into its dominating $d\text{−}p$- and $d\text{−}f$-contributions as a function of the photon energy. The energy of the initial state has been fixed to $-2\mathrm{eV}$ with respect to the Fermi energy.

Figure 4

Decomposition of the theoretical spin-difference of the photo current $\Delta I_{+}=I_{+}^{\uparrow }-I_{+}^{\downarrow }$ of Au according to the angular momentum character of the initial and final states for various photon energies. Only the dominating $d\text{−}p$ (dotted line) and $d\text{−}f$ (full line) contributions are shown.