We propose here a systematic and straightforward way to include point-group
symmetries into the theory of photoelectron diffraction. In addition to re
ducing the number of scattering path operators that have to be calculated,
this approach permits as well as to derive a new algorithm to minimize the
number of paths that have to be explored in the series expansion cluster me
thod by making use of path degeneracies. (C) 2001 Elsevier Science B.V. All
rights reserved.