The wave packet dynamics accompanying the excitation to a decaying electronic state and the subsequent decay to final electronic states are discussed. The cross sections for the excitation and for the production of final states are related to the corresponding wave packets. The time-dependent formulation adds insight into the process and is amenable to semiclassical approximations and interpretations. It can also be used to compute the gross features of the observed spectra via a spectral moment expansion. An illustrative application demonstrates the usefulness of the expansion.