A model of charge separation reactions including charge exchange between fragments is developed to include sequential reactions. The model uses known molecular structures, assumes an exponential distribution of intermediate lifetimes, and requires a mean lifetime as the only disposable parameter. The general predictions and quantitative calculations of relative intensities, peak widths, and peak shapes are shown to agree with photoelectron-photoion-photoion coincidence spectra of HN3, ClN3, and IN3 and other small molecules studied previously.