Experimental determination of bulk energy band dispersions.

This paper reviews the methods of determining energy band dispersions in a tutorial way. Angle resolved photoemission techniques are applied that take advantage of a polarized tunable light source like synchrotron radiation. Various approximations (including exact methods) are described that have been made to obtain energy band dispersions (E vs k) directly from experiment, using a simple three-step model of photoemission. Apart from the energy E and the momentum k, there are symmetry quantum numbers of electron states in a crystal, which can be determined by using polarization selection rules. Examples are discussed for various methods and materials. In conclusion, the theoretical and practical limits of the band structure concept are considered.