The symmetry of the Be(0 0 0 1) surface states as determined by ARPES with variable polarization synchrotron radiation

We measured the electronic band structure of the Be(0 0 0 1) surface using high-resolution angle resolved photoemission with variable polarization synchrotron radiation. We used photons of 32.5 eV delivered by the beamline APE at Elettra, with the two orthogonal linear polarizations. The electronic band structure along the two ( over(Γ, -) s(-) over(K, -) and over(Γ, -) s(-) over(M, -) ) high symmetry directions was probed. As a function of photon polarization either states of even or odd symmetry with respect to the crystal reflection plane(s) contribute to the photoemission intensity. We find that the two surface states have different reflection symmetry, according to the theoretical predictions.