  It is widely accepted that in molecular systems the nuclear interaction plays
a negligible role, because of the strong Coulomb repulsion of the nuclei at
small distances. We are going to show that this is not always true. The
existence of an extended nuclear resonance may lead to considerably enhanced
nuclear reaction rates in appropriately prepared molecules. Especially we point
out that p+p+ ^{16}O, i.e., the constituents of water, can form a ^{18}Ne(1^-)
threshold resonance which decays under energy release into ^{17}F and a proton.
