Properties of the low-lying positive-parity states in Be and C

Excitation energies and electromagnetic form factors of the low-lying positive-parity states have been calculated in⁹Be and ¹³C on the basis of a particle-core coupling model. The results are compared with recent electron scattering experiments and photon data. The first excited levels in the two nuclei show a large contribution from the spin term of the electromagnetic interaction at low-momentum transfer q² < 0.6 fm⁻².