Charge migration is a fundamental and important process in the photochemistry of molecules and has been explored by time-resolved photoelectron angular distributions. A scheme based on UV pump and polarized soft X-ray probe techniques shows that photoelectron diffraction effects enable us to reconstruct electronic coherences encoding the information of the charge migration with extreme time resolutions. We discuss how probe pulse helicity influences the probing photoelectron spectra in the presence of molecular nonspherical Coulomb potentials. This phenomenon is analyzed theoretically and simulated via ab initio calculations for the molecular hydrogen ion, offering a reliable approach for measurements of charge migration and for the exploration of molecular structure in attosecond science.