Spectral distribution calculations of the level density and spin-cutoff parameters ofSi28

Spectral distribution calculations of the separate positive and negative parity level densities and spin cutoff parameters for ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$ have been made in an $\mathrm{sdf}$ basis. A configuration expansion utilizing higher moments of the Hamiltonian is found to be important in improving agreement between calculation and experiment at low excitation energies. The Hamiltonian moments were corrected for the effects of spurious c.m. motion. The present results suggest that spectral distribution calculations can yield level densities which agree with experimental information on the number of levels, spin cutoff factors, and parity ratios over an energy range of over 20 MeV.