Plasmon dispersion in Beryllium

We have measured the plasmon dispersion in polycrystalline Beryllium at wave vectors up tok=1.29 Å^?1 with electron energy loss spectroscopy. The plasmon energy is 18.8±0.1 eV, the fitted quadratic dispersion coefficient is α=0.36±0.03 for 0<k<1.29 Å^?1 and α _L =0.52+0.04 fork<0.55 Å^?1. We compare our results with the plasmon dispersion in other simple metals and point out discrepancies with the theories of the homogeneous electron gas.