Inelastic excitation of 12C and 14N by 122 MeV protons and implications for the effective nucleon-nucleon interaction

Cross sections for the 12C( p,p')12C and 14N( p,p')14N reactions have been measured at E/sub p/=122 MeV. Scattered protons were momentum analyzed in a dispersion-matched magnetic spectrograph and detected in a helical-cathode position-sensitive proportional counter. Transitions to states in 12C at 4.44 MeV (2+,T=0), 12.71 MeV (1+,0), 15.11 MeV (1+,1), 16.11 MeV (2+,1), and in 14N at 2.31 MeV (0+,1) and 3.95 MeV (1+,0), are very useful for studying the spin-isospin dependence of the effective two-nucleon interaction. Cross sections for these states from the present experiment and from earlier measurements at 185 MeV have been analyzed in the distorted-wave impulse approximation. Simultaneous consideration of (e,e') data for the same transitions helped to disentangle some nuclear-structure and reaction-mechanism effects. The distorted-wave impulse approximation provides a good description of those transitions in 12C mediated predominantly by the S=T=1 part of the effective interaction and also gives a reasonable description of the S=T=0 transitions in both nuclei. The mechanisms for excitation of the 12.71-MeV state in 12C (S=1, T=0) and the 2.31-MeV state in 14N (S=1, T=1) remain a puzzle