Systematics of Coulomb-Distortion Effects in Large-AngleM1Electroexcitation

Abstract

Computer calculations of inelastic electron scattering for $M1\mathrm{}$ transitions in light nuclei are carried out for very low-energy electrons, $E_0<5\mathrm{}$ MeV, and low-energy electrons $10<\mathrm{}{E}_0<70\mathrm{}$ MeV. The calculation is a partial-wave analysis using the Duke program. Computer results are presented graphically as the Coulomb distortion versus $Z$, $E_0$, $k$, and $\theta$. The dependence of the assumed nuclear model on the calculation is examined. Numerical results are presented leading to a revision of the radiative width ${\Gamma }_0$ for the 15.1-MeV state of ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$. Revised widths are presented for other $M1\mathrm{}$ transitions in ${}_{}{}^{10}{}_{}{}^{}\mathrm{B}$, ${}_{}{}^{26}{}_{}{}^{}\mathrm{Mg}$, and ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$. With regard to the ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ width, the present status of the conserved-vector-current test in ${}_{}{}^{12}{}_{}{}^{}\mathrm{B}$, ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, and ${}_{}{}^{12}{}_{}{}^{}\mathrm{N}$ is discussed. Finally, the numerical significance of Coulomb effects in the $M1\mathrm{}$ breakup of the deuteron by electrons with $E_0<100\mathrm{}$ MeV is presented. The small Coulomb-distortion effect is compared with estimates of meson exchange currents in $\mathrm{D}(e, e^{\prime })np$.