Angle Resolved Photoemission Spectroscopy
By measuring the kinetic energy (E) and momentum (k) of the electron in vacuum, the dispersion of the electron state E(k) in the solid can be determined
EF = Fermi energy
Evac = Vacuum level
Ei , ki= initial energy and momentum of electron in solid
Ef , kf = final energy and momentum of electron following excitation
E, k = energy and momentum of free electron in vacuum after emission
Φ = Evac – EF = work function
hν = incident photon energy
Energy conservation gives E(k) = hν – Φ – Ei(ki)
Momentum conservation parallel to the surface gives:
Momentum is not conserved perpendicular to the surface, but for a given inner potential V0, we can write:
