Occupied and unoccupied electronic states of Cu(110) were investigated with angle-resolved two-photon photoemission spectroscopy with an energy resolution of 30 meV. The high energy resolution enables the individual $n$ $=$ 1 and 2 image-potential-derived structures to be distinguished. The $n$ $=$ 1 structure was 0.85 eV below $E_{\mathrm{vac}}$ at $\mathrm{\Gamma ̄}$. The effective mass of the electron for the structure was the same for both dispersions along the $\mathrm{\Gamma ̄}\mathrm{X̄}$ and $\mathrm{\Gamma ̄}\mathrm{Ȳ}$directions within the experimental error. The $n$ $=$ 2 structure appeared in the $L_{2^{\prime }}$-$L_1$ gap along the $\mathrm{\Gamma ̄}\mathrm{Ȳ}$ direction, and it did not appear at $\mathrm{\Gamma ̄}$, or along the $\mathrm{\Gamma ̄}\mathrm{X̄}$ direction, which means that the $n$ $=$ 2 structure was strongly affected by the bulk band. In this paper, other two-photon photoemission structures and dispersions are compared with results reported in the previous literature.

• Received 3 November 2010

DOI:https://doi.org/10.1103/PhysRevB.83.245410