The electrostatic resonance of ions can be observed in conditions of strong electron depletion in plasma regions that are small compared with the Debye length, and in conditions of very low degrees of ionization when most electrons are attached to neutral molecules. If observed, this resonance is expected to be broadened by collisions with the background gas. In the limit of collision frequencies, large compared to the resonance frequency, the ion plasma resonance again becomes sharper, albeit at a lower (effective) frequency, corresponding to a collective motion of ions and neutrals of the ion-acoustic wave type. A straightforward simple calculation suggests the possibility of this type of resonance under experimental conditions, which have led to neutron emissions from resonant plasma formations that are interpreted as plasma cavitons.