Transitions in Zr, Hf, Ta, W, Re, Hg, Ac and U ions with high   sensitivity to variation of the fine-structure constant
  We study transitions between ground and low-energy excited states of heavy ions corresponding to s-d single-electron transitions or s^2-d^2 double-electron transitions. The large nuclear charge Z and significant change in angular momentum of electron orbitals make these transitions highly sensitive to a potential variation in the fine-structure constant, alpha. The transitions may be considered as candidates for laboratory searches for space-time variation of alpha. 
J. C. Berengut, V. A. Dzuba, and V. V. Flambaum
physics.atom-ph