Spin cutoff parameters for 28Si, 29Si, and 30P: Comparison of measurements with spectral distribution calculations

Spin cutoff parameters for 28Si, 29Si, and 30P have been deduced from angular distribution measurements for (α,n) reactions on 25Mg, 26Mg, and 27Al. Calculations of the spin cutoff parameter which include the effect of two body interactions are made using the theory of spectral distributions. The results obtained by dividing the space into subspaces and expanding the strength distribution of each in a Gaussian are found to be more reliable than calculating a single Gaussian for the entire space. The comparisons in this study indicate a need for the inclusion of higher moments of the Hamiltonian in the level density expansion