Is there large weak mixing in heavy nuclei?

Recent results in parity non-conserving neutron-nucleus scattering show a tendency for the parity non-conserving effects to predominantly have the same sign. Explanations of this phenomenon all require a weak matrix element between single-particle levels in heavy nuclei to be ∼100 eV. This paper contains a discussion of this effect and how the same phenomenon will manifest itself in other systems. The gamma decay of 207Pb is given as an example of a system where the weak matrix element between single-particle levels in a heavy nucleus can be measured directly