Zero-kinetic energy states are highly stabilized Rydberg states that reside below each ionic eigenstate of a molecular system. The high resolution detection of these states constitutes a high resolution spectroscopy for molecular ions. Zero-kinetic energy states are produced from optically pumped Rydberg states. Such Rydberg states, once produced, are found to either decay in the presence of fields or be converted to zero-kinetic energy states in the presence of ions. A simple mechanism is proposed based on these experimental results for the range of fields and ion concentrations investigated. The experiments were performed with pulsed and static electric fields of different magnitudes at various ion concentrations. The results reconcile many previously reported observations and suggestions concerning the differences between molecular and atomic (and/or small molecule) zero-kinetic energy states and lead to a unified picture for the production of zero-kinetic energy states.