The importance of electronic correlations for the calculation of X-ray and fast electron scattering by Ne(1S)

The elastic, inelastic and total intensities of diffraction for fast electrons, the coherent, incoherent and total scattering for X-rays by the neon atom in its ground state have been studied using the atomic Bethe- Goldstone equations which give about 97.3% of the empirical correlation energy. The results are compared with those obtained with two CI wavefunctions and the Clementi wavefunction which give respectively 85% 53% and 20% of the correlation energy. The authors give also the Hartree- Fock results. It is shown that a properly correlated wavefunction is necessary when one wants to compare carefully the theoretical and experimental scattering intensities.