  We report a detection of differences in ion and neutral velocities in
prominences using high resolution spectral data obtained in September 2012 at
the German Vacuum Tower Telescope (Observatorio del Teide, Tenerife). A time
series of scans of a small portion of a solar prominence was obtained
simultaneously with a high cadence using the lines of two elements with
different ionization states, namely the CaII 8542 A and the HeI 10830 A.
Displacements, widths and amplitudes of both lines were carefully compared to
extract dynamical information about the plasma. Many dynamical features are
detected, such as counterstreaming flows, jets and propagating waves. In all
the cases we find very strong correlation between the parameters extracted from
the lines of both elements, confirming that both trace the same plasma.
Nevertheless, we also find short-lived transients where this correlation is
lost. These transients are associated with the ion-neutral drift velocities of
the order of several hundred m/s. The patches of non-zero drift velocity show
coherence on time-distance diagrams.
