Why phase errors affect the electron function more than amplitude errors.
If Fexp(ialpha) are the set of structure factors for a structure f, the amplitudes can be converted to those of an uncorrelated structure g (amplitude swapping) by multiplying each F by the positive number G/F. Correspondingly, the image f is convoluted with k, the Fourier transform of G/F; k has a large peak at the origin, so that f * k approximately f. For swapped phases, the image f is convoluted with l, the Fourier transform of exp(iDeltaalpha), where Deltaalpha, the phase difference between F and G, is a random variable; l does not have a large peak at the origin, so that f * l does not resemble f. The paper provides quantitative descriptions of these arguments.
Lattman
Eaton
E
Thomas C. Jenkins Department of Biophysics, the Johns Hopkins University, Baltimore, MD 21218, USA.
DeRosier
David
D
D003461:Crystallography / Q000379:methods*; D005583:Fourier Analysis; D008962:Models, Theoretical