  It is demonstrated that the ionization events in the vicinity of a small
floating grain can increase the ion flux to its surface. In this respect the
effect of electron impact ionization is fully analogous to that of the
ion-neutral resonant charge exchange collisions. Both processes create slow ion
which cannot overcome grain' electrical attraction and eventually fall onto its
surface. The relative importance of ionization and ion-neutral collisions is
roughly given by the ratio of the corresponding frequencies. We have evaluated
this ratio for neon and argon plasmas to demonstrate that ionization enhanced
ion collection can indeed be an important factor affecting grain charging in
realistic experimental conditions.
