content_image/328934.jpg
<img src='content_image/328934.jpg'>

the non-linear dispersion away from ¯ K . The photoemission intensity around this triangular contour shows strong variations which are caused by the interference effect and very similar to the results obtained for the valence π -band of graphite and graphene [4, 5]. 

As already expected from Fig. 3(b) and (c), the interference effect is even stronger for emission from the bonding and anti-bonding states at ¯ Γ (see Fig. 3(d) and (e)). The intensity variations of both bands are almost opposite to each other: for some ¯ Γ points only the bonding band is observed, for others only the anti-bonding band. For normal emission this is easy to understand: for the bonding band the wave functions centred on the two atoms in the unit cell emit in phase and this band is observed. For the anti-bonding wave function, the two atomic wave functions emit out of phase, thus suppressing the photoemission. 

