  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.
