Cooper minima in the transitions from low-excited and Rydberg states of   alkali-metal atoms
  The structure of the Cooper minima in the transition probabilities and photoionization cross-sections for low-excited and Rydberg nS, nP, nD and nF states of alkali-metal atoms has been studied using a Coulomb approximation and a quasiclassical model. The range of applicability of the quasiclassical model has been defined from comparison with available experimental and theoretical data on dipole moments, oscillator strengths, and photoionization cross-sections. A new Cooper minimum for transitions between rubidium Rydberg states has been found. 
I. I. Beterov, C. W. Mansell, E. A. Yakshina, I. I. Ryabtsev, D. B.   Tretyakov, V. M. Entin, C. MacCormick, M. J. Piotrowic...
physics.atom-ph