 Because of this, and its pronounced surface sensitivity, the technique is best suited for the complete characterization of the band structure in low-dimensional systems, but is widely used for three-dimensional materials as well.For those, the perpendicular component of the wave vector is usually approximated with the assumption of a parabolic, free-electron-like final state with the bottom at energy formula_13 and is parameterized as formula_14.A typical instrument for angle-resolved photoemission consists of a light source, sample holder attached to a manipulator, and an electron spectrometer that are all part of an ultra-high vacuum system which provides necessary protection from adsorbates for the sample surface, and eliminates scattering of the electrons on their way to the analyzer.