Dependence of heavy-ion neutron transfer on distance and spin

We review the ''slope anomaly'' data for 2-neutron transfer between heavy ions. Where one or both partners are deformed, the 2-neutron transfer always shows about the same dependence on distance-of-closest approach D as does 1-neutron transfer. Where both partners are spherical, the 2-neutron transfer falls off as the square of the 1-n transfer with one known exception 208Pb(64Ni,62Ni)210Pb. We propose that the enhancement of 2-n transfer comes from the pairing attraction between the neutrons and that the enhancement requires availability of high-l orbitals to form a tight wave packet in angle. A simple model is derived for numerical estimation. Prospects for testing Coriolis antipairing by heavy ion 2-n transfer are re-examined. 10 refs., 3 figs