We have calculated the ground-state occupancies of various nuclei in the spectroscopic space of upperf-p shell andg_9/2 orbit using spectral distribution methods. The modified fully renormalised Kuo-Brown interaction has been used. The calculated values have been compared with the experimental results.

A new derivation of the inverse energy-weighted sum-rules is given by applying the spectral distribution methods to the Rayleigh-Schrodinger perturbation theory. The scalar space result is then extended to the configurations. This is applied to obtain corrections to the ground-state energy estimates when the effective interaction is approximated by a model Hamiltonian obtained by taking linear combinations of various parts of the pairing and the Q.Q operators.