The lifetimes and decay energetics of intermediates have been studied by measuring the velocity and angular distributions of heavy-Rydberg ion pair states formed through electron transfer in thermal-energy collisions between Rydberg atoms and attaching targets. The analysis of the experimental results by using Monte Carlo simulations indicates that electron attachment to CF3I and CH2Br2 forms very-short-lived intermediates whereas electron capture by CCl4 produces a long-lived intermediate.