Large nondipole parameters with strong correlation effects in photoelectron angular distributions at kilo-electron-volt energies

Strong correlation in quadrupole photoionization amplitudes, along with strong correlation in dipole photoionization amplitudes, is found at keV photon energies. As a result, correlation is shown to profoundly influence the E1-E2 nondipole photoelectron angular distribution parameters, which themselves are found to be large. An approximate cancellation of correlation effects for measurements made using a certain geometry is demonstrated. Suggestions for future measurements to spotlight correlation in nondipole effects are indicated.