  Angle-resolved photoemission spectroscopy (ARPES) measures the interference
of dipole allowed Coulomb wavelets from the individual orbital emitters that
contribute to an electronic band. If Coulomb scattering of the outgoing
electron is neglected, this Huygens view of ARPES simplifies to a Fraunhofer
diffraction experiment, and the relevant cross-sections to orbital
Fouriertransforms. This plane wave approximation (PWA) is surprisingly
descriptive of photoelectron distributions, but fails to reproduce kinetic
energy dependent final state effects like dichroism. Yet, Huygens principle of
ARPES can be easily adapted to allow for distortion and phase shift of the
outgoing Coulomb wave. This retains the strong physical intuition and low
computational cost of the PWA, but naturally captures momentum dependent
interference effects in systems that so far required treatment at the ab initio
level, such as linear dichroism in Rashba systems BiAg2 and AgTe.
