Negative-ion-negative-ion neutralization-reionization (−NR−)

There are four neutralization‐reionization processes which can be studied. In the first two, gaseous cations are collisionally reduced and the resulting fast neutrals are either oxidized by collisional electron removal (NR) or reduced further by collisional electron attachment (NR−). In the third and fourth processes, gaseous anions are collisionally oxidized and the resulting fast neutrals are either oxidized further by collisional electron removal (−NR) or reduced by collisional electron attachment (−NR−). These four processes are illustrated briefly using the interrelated species [SF5]+ and [SF5]−. Negative‐ion‐negative‐ion neutralization‐reionization (−NR−) processes are illustrated for [CH3O]−, [C2H5O]−, [CO3]− and [HCO3]− and compared with −NR processes. In addition, collisional electron attachment ionization of fast neutrals formed in unimolecular fragmentation of cations is illustrated. The −NR− studies of [CO3]− and [HCO3]− show that both CO3 and HCO3 are stable neutral species with lifetimes greater than 0.7 μs.