  Excitation energy spectra and absolute cross section angular distributions
were measured for the 13C(18O,16O)15C two-neutron transfer reaction at 84 MeV
incident energy. This reaction selectively populates two-neutron configurations
in the states of the residual nucleus. Exact finite-range coupled reaction
channel calculations are used to analyse the data. Two approaches are
discussed: the extreme cluster and the newly introduced microscopic cluster.
The latter makes use of spectroscopic amplitudes in the centre of mass
reference frame, derived from shell-model calculations using the Moshinsky
transformation brackets. The results describe well the experimental cross
section and highlight cluster configurations in the involved wave functions.
