The typical extraction potential used in MALDI MS is in the order of 10 6 V/m. Using 2.1 × 10 6 V/m as an example, the force exerted on a unit charge by the potential is 3.4 × 10 - 13 N (see supporting information). The attraction force between two opposite unit charges is 2.5 × 10 -10 N assuming a distance of 1 nm between the unit charges. Therefore, without the assistance of thermal energy of ion pairs, the ion extraction potential would not be sufficient to separate the ions in an ion pair. If Pauling repulsion force between the ions at the 1 nm distance and beyond were considered, the required force for the ion separation would be lower than 2.5 × 10 -10 N. However, Pauling force decreases far more sharply with the increase of distance than the Columbic force, the repulsing force can hardly change the result. Based on these considerations, if separation of the charges solely by the ion extraction potential were desired, the distance between the two opposite unit charges would need to be 26 nm or longer.