  Laser-induced fluorescence (LIF) performed on metastable ions is frequently
used to probe the dynamics of ground-state ion motions in many laboratory
plasmas. However, these measurements place restrictions on the metastable ion
lifetime. Metastable states are produced from direct ionization of neutral
atoms as well as ions in other electronic states, of which the former will only
faithfully represent processes that act on the ion dynamics in a time shorter
than the metastable lifetime. We present here the first experimental study of
this type of systematic effect using wave-particle interaction in an argon
multidipole plasma. The metastable lifetime and relative fraction of
metastables produced from preexisting ions, necessary for correcting the LIF
measurement errors, can be determined by fitting the experimental results with
the theory we propose.
