Effect of correlation on the mean excitation energy of beryllium

Abstract
Using the polarization-propagator formalism, the dipole-oscillator-strength distribution for Be has been calculated. Comparison of correlated with Hartree-Fock results shows that inclusion of correlation is very important for calculation of properties of the dipole-oscillator-strength distribution. In particular, I0 is calculated to be 43.6 eV, some 12% higher than previously reported.