Three Surface Resonances on the (100) Face of W and Mo: An Angle-Resolved Synchrotron Photoemission Study

We have studied the surface resonances on Mo(100) and W(100) with angle-resolved, $\hslash \omega$-dependent photoemission using synchrotron radiation. For normal emission, two resonances are seen. They are located 0.3 and 3.3 (0.4 and 4.2) eV below $E_{\mathrm{F}}$ for Mo (W). The high-lying resonance remains symmetric and narrow for all photon energies used. Its intensity peaks at $\hslash \omega =15\mathrm{} \mathrm{and} 30 \left(14\mathrm{} \mathrm{and} 29\right)$ eV for Mo (W). For $\theta >~2°$, a second highlying resonance appears a few tenths of an eV below the first one. Many-body phenomena are not required to explain the data.