Theoretical simulation of beam-foil decay curves for resonance transitions of heavy ions

A systematic study of the influence of cascades on heavy-ion beam-foil decay curves has been made. Using theoretical data for the lifetimes and initial populations of excited states, decay curves simulating beam-foil excitation conditions have been constructed for the resonance transition of three ions in the copper isoelectronic sequence. Various models for the initial population distribution were tested by comparison with a detailed beam-foil decay curve available for Krviii. We found that customary exponential-fitting methods were not able to extract the primary lifetimes from the simulated curves used in constructing them, although the replenishment ratios were close to zero. General implications of this subtle masking of the primary lifetime by numerous cascades for the accuracy of experimental beam-foil data are discussed, especially for $\Delta n=0\mathrm{}$ transitions in heavy ions.