Cross sections and complex phase shifts for the scattering of protons from 12C at the 8.20 MeV and 9.14 MeV anomalies

Abstract

Absolute differential cross sections as a function of angle for the elastic scattering of protons from 12C and for the inelastic scattering reaction 12C(p, p′) 12C ∗ ( Q = −4.43 MeV) were measured at incident proton energies of 8.20 MeV and eleven energies between 9.10 and 9.26 MeV. Complex phase shifts were obtained to represent the elastic scattering cross sections and the total inelastic cross sections. The complex phase shift analysis has confirmed the J π = 3 2 − assignment at the 8.20 MeV anomaly and 7 2 − and 5 2 − for the stronger and weaker state at the 9.14 MeV double anomaly, respectively. These assignments were used in a calculation which reproduced the features of the elastic scattering cross sections as a function of energy over the 9.14 MeV doublet. An examination of the behaviour of the phase shifts over the anomaly revealed that the total phase shift for the f 5 2 partial wave does not pass through 90° whereas the total phase shift for the f 7 2 partial wave does pass through 90°.