180 degrees electron scattering from 14C.

Abstract

Inelastic electron scattering cross sections for $^{14}\mathrm{C}$ have been measured at a scattering angle of 180\ifmmode^\circ\else\textdegree\fi{}, with incident beam energies ranging from 81.9 to 268.9 MeV. Transverse form factors were measured for transitions to low-lying natural-parity states, to unnatural-parity ``stretched'' ${J}^{\ensuremath{\pi}}$${=4}^{\mathrm{\ensuremath{-}}}$ states, and to the ${J}^{\ensuremath{\pi}}$${=2}^{\mathrm{\ensuremath{-}}}$ analog to the $^{14}\mathrm{B}$ ground state. Cross sections for ${4}^{\mathrm{\ensuremath{-}}}$ states at 11.7 and 17.3 MeV are combined with pion scattering data to determine the isoscalar and isovector transition amplitudes. Form factors for other states are compared to shell-model calculations. From the excitation energy of the newly discovered ${J}^{\ensuremath{\pi}}$T${=2}^{\mathrm{\ensuremath{-}}}$2 state at 22.1 MeV, the $^{14}\mathrm{\ensuremath{-}}^{14}$B Coulomb energy difference is determined to be 2.25\ifmmode\pm\else\textpm\fi{}0.10 MeV.