OCCUPATION PROBABILITIES OF SHELL-MODEL ORBITALS

A number of observations including absolute spectral functions from (e,e′p) reactions indicate occupancies of shell-model orbitals substantially below unity, e.g. about 50% in 208Pb where many-body theories predict values ranging from 60 to 90%. We present the CERES method (combined evaluation of relative spectroscopic factors and electron scattering) for the determination of occupancies which avoids the questionable use of absolute spectroscopic factors and accounts for experimental cut-offs in the spectroscopic sums. The method is applied to the Pb-region where a network of interrelated relative spectroscopic factors from (d,3He), (e,e′p) and (3He,d) reactions has been established and combined with electron scattering results. For the 3s-proton shell in 208Pb an occupancy of about 85% is obtained. It is pointed out that this does not contradict the 50% value derived from truncated sums, provided short-range correlations produce long tails in the spectral functions. © 1990.