Low energy dipole modes in C-14, Be-12 and Li-11, Coulomb dissociation of Li-11

We have performed a calculation of the low energy dipole modes in C-14, Be-12 and Li-11 using a two-neutron pairing model. The lowest 1(-) states of C-14 are well described by the model and two 1(-) states are predicted with 2.7 and 4.3 MeV excitation energies in Be-12. In Li-11 we obtain a large enhancement of the dipole strength at <(E)over tilde (d)> = 1.2 MeV close to the energy of the ''soft dipole resonance'' seen in experiments with a B(E1) = 1.2-1.3 e(2)fm(2) if, and only if, we assume a low energy (0.1-0.2 MeV) s-resonance in Li-10. Simultaneously we have studied the two-neutron Coulomb dissociation of Li-11 by several targets and have obtained under the same assumption good agreement with the values determined from experiments for a lead target. (C) 1997 Elsevier Science B.V.