Anomaly in the Energy Dependence of the Angular Distributions for Deuterons Scattered from Mg24 in the Energy Range from 6 to 13 MeV

Angular distributions for elastic and 2+ inelastic deuteron scattering from Mg24 have been obtained at various energies in the range from 6 to 13 MeV. Yield functions have been measured in 50 keV steps at 90° and 150°. In the region from 10 to 13 MeV, the elastic angular distributions show an anomalous behavior : instead of moving in from 180°, a new maximum is created by the breakup of a broad maximum at about 100° into two maxima. The inelastic angular distributions do not show such an anomalous energy dependence. Therefore the Blair phase rule between the elastic and the 2+ inelastic angular distributions breaks down in the energy region of the anomaly in the elastic scattering, but it holds outside this energy region. In spite of fluctuations in the excitation functions, an optical-model analysis of the elastic angular distributions yields parameters which, with the exception of W, vary smoothly with energy.