As the heaviest simple atom, francium could give the most precise measurements. The Stony Brook experiment is the first step toward such measurements. The signature of the weak interaction is the possibility of an electric dipole transition between two states of the same parity, in violation of the selection rules allowed by the electromagnetic interaction. Such an observation would probe our understanding of the standard model of fundamental interactions with much smaller momentum transferred than at high energy accelerators. This makes francium a laboratory where we can study fundamental interactions.
Interesting possibilities can also arise when a sample of polarized radioactive atoms decay.
The spatial distribution of decay alpha particles can carry information about the nuclear structure. If the decay is through beta particles then further information on weak processes is possible.