The Spin-Flip Scattering of High Energy Protons by Light Nuclei

Abstract

The spin-flip inelastic scattering of high energy protons is investigated for the 15.1 Mev excitation of C12 ancl the 9.2 Mev excitation of N14. The electromagnetic interaction is found to be far too weak to account for the observed cross sections. The spin-flip cross sections clue to the (rr1 ·<r2) (-r1 part of the nuclear interaction are calculated by means of the impulse approximation. In the case of C12 the cross section can l1e calculated without referring to any special nuclear model from theft-value of the fl-clccay of B12 or N 12 to the ground state of C12. The result agrees very well with the experimental cross section showing the validity of the assumptions involved in the calculation. It is also shown that the spin-flip scattering is the only process which shows the angular distribution with maximum at Oo leaving the residual nucleus in a discrete low-lying excited state. The nuclear matrix element of the transition estimated conversely from the observed cross section may be used as a datum: for the relevant nuclear states. In particular the separate contributions of the spin and the orbital angular momenta to the M1 r-transition between the relevant states can be estimated and are found to be of the ratio 1 to 0.3 both for C12 and NI4. Discussions arc given on the approximations used in the calculations as well as on the nuclear states relevant to the excitations.