Quadratic sheaves and self-linkage

Generalizing an old result proved by P. Rao [see MR 83i:14025] for arithmetically Cohen-Macaulay, self-linked subschemes of codimension 2 in the projective n-space P, we give a characterization of self-linked pure subschemes of codimension 2 in P satisfying a necessary parity condition, in characteristic different from 2. We make use of the theory of quadratic sheaves described in a previous paper of the authors [see MR 99h:14044].