  The nuclei 11Be and 11Li provide paradigmatic examples of one-and two-
neutron halo systems. Because the reaction 1H(11Li,9Li)3H is dominated by
successive transfer, one can use the quantitative picture emerging from a nu-
clear field theory description of the structure and reaction mechanism of the
above Cooper pair transfer process and of the 2H(10Be,11Be)1H and
1H(11Be,10Be)2H reactions, to shed light on the structure of 10Li. This
analysis provides important support for a parity inverted scenario with a 1/2+
virtual state at about 0.2 MeV.
