Electronic band structure of metallic calcium measured by electron momentum spectroscopy

We have measured the bulk energy-momentum resolved conduction band structure of metallic calcium using electron momentum spectroscopy (EMS). From the EMS data we have extracted the band dispersion, occupied bandwidth and density of states. The experimental results are compared with band structure calculations performed within the linear muffin-tin orbital (LMTO) approximation. The free-electron parabola expected for the dispersion relation in a metallic solid is clearly reproduced in the experimental data and is in good agreement with our calculation A background produced by multiple-scattering events within the target is also evident in the EMS results. In order to make a quantitative comparison, we have included the effects of multiple scattering in the calculation using a Monte Carlo (MC) simulation. The results of this procedure reproduce the measured conduction band features and background intensity very well. The occupied bandwidth is measured to be 3.3+/-0.2 eV, and agrees with previous measurements and the value predicted by our LMTO calculation when the MC simulation is included. However, the experiment indicates that the band dispersion curve is narrower in momentum by as much as 0.1 au compared with the theory. We have also made measurements of the energies of the 3s and 3p core levels in metallic calcium, and obtained values of 45.0+/-0.4 eV and 25.6+/-0.2 eV respectively. These results are in good agreement with previous experiments.