M. H. Macfarlane

Gamow-Teller sum rules and ground-state correlations

Abstract New sum rules are derived for separate total (n,p) and (p,n) Gamow-Teller strengths and are used in an analysis of the total GT strength and the ground-state occupation-number distribution in 208 Pb.

Some implications of a two-component reduction of Dirac phenomenology☆

Abstract A two-component reduction of Dirac wavefunctions and operators is used to identify situations where Dirac and Schrodinger phenomenology differ significantly. In this two-component form pseudovector and pseudoscalar coupling operators differ in a fashion that reduces the pseudovector coupling strength in the nuclear medium. This reduction promises to improve agreement between theory and experiment for various nuclear direct reactions.

The orbital magnetic dipole response of nonspherical nuclei

Abstract We discuss experimental facts and theoretical models of the isovector M1 response in nuclei. The three isospin components ( T 2 = −1, 0, 1), orbital and spin components are identified and introduced by isospin decomposition of the nuclear M1 operator. Microscopic descriptions of the low-lying orbital ΔT 2 = 0 excitation are given. The collective interpretation of this mode is discussed in some detail with the conclusion that though it is an isovector rotational oscillation, a small but important shape vibrational admixture is present, allowing rotation without separation of the proton and neutron densities, in contrast to the scissors mode visualization.

The sensitive radius — spatial localization in heavy-ion reaction analyses

Abstract Heavy-ion elastic scattering can be sensitive only to averages of the interaction potential over distances comparable to or greater than the wavelength of the relative motion. Sharply-defined “sensitive radii” emerge only when the assumption of a definite functional radial dependence imposes a relation between average- and point-values of the potentials.

Monte carlo methods for nuclear reactions

Abstract We develop a Monte Carlo method without partial-wave decomposition for nuclear-reaction calculations. The n th order Born series for the T matrix is simulated by averaging over n -step random walks in momentum space. The Born series is summed by Pade transformation. We test the method in two applications; to nucleon-nucleon scattering and to low-energy pion-nucleus scattering.