10 developed in-house. It allows fast acquisition of the spectra in snap-shot mode, with up to thousand data points in each spectrum and in as short as 80 ms/spectrum. The data shown in Fig. 2 are acquired in scanning mode at hν =350 eV, 400 eV and 700 eV, while in snap-shot mode at 500 eV and 600 eV. The fast scans, with a total of 420 spectra that fill 1/3 of the emission hemisphere, take less than 30 min. At the other photon energies more spectra were taken: 2270 at hν = 700 eV, 820 at hν = 400 eV and 1300 at hν = 350 eV. Such scans take several hours. The photon energy was calibrated by the absorption edges of gas-phase Ar, Ne and N$_{2}$. The manipulator used in the experiments is a modified version of the VG-CTPO with fully computer-controlled polar and azimuthal rotations. For the analysis of the data all the spectra taken at one photon energy were first aligned to the Fermi level of the Ir substrate, then they were fitted with the same line shape parameters but the binding energy was left free in the fit. Fits for two spectra are shown in Fig. 1(f). The actual peak fits were made using a Doniach-Sunjic line profile [12] with a Lorentzian width of 130 meV, an asymmetry parameter of 0.093, a Gaussian width depending of the photon energy and a linear background. The narrowest Gaussian width was 165 meV and this could be used for photon energies up to 400 eV. It is the value used for the two fits shown in Fig. 1. Note, however, that the spectra were measured and fitted in a wider range than displayed in Fig. 1. We have observed a small variation of the lineshape over the entire data set taken at any given photon energy. However, a good fit to all the spectra can be obtained with one set of parameters describing the line shape. Arbitrariness in the exact values of these parameters induces a small uncertainty in the absolute degree of binding energy modulation of about 5 meV. We thus estimate the total uncertainty of the observed bandwidth to be of the order of 10 meV. The modulation functions in Fig. 1(h) and the left part of Fig. 2 were obtained for each polar emission angle Θ from the peak intensity I (Θ , φ ) as ( I (Θ , φ ) − I$_{0}$ (Θ)) /I$_{0}$ (Θ), were I$_{0}$ (Θ) is the average value of each azimuthal scan. Note that no artificial symmetry was imposed on the data. The experimental modulations are as symmetric as they appear, greatly enhancing out confidence in the data. The calculated modulations in Fig. 2 were obtained in the same way. The potoemission intensity calculations used to obtain the calculated modulation func- tions in Fig. 2 were performed by the program package for Electron Diffraction in Atomic Clusters (EDAC) [13]. The photoemission intensity at each emission angle was calculated