We report results from a study of the integrated column density and
expansion dynamics of ground-state-selected Ba+ ions in a
laser–plasma plume using a new experimental system—VPIF
(vacuum-ultraviolet photoabsorption imaging facility). The ions are
tracked by recording the attenuation of a pulsed and collimated vacuum
ultraviolet beam, tuned to the 5p–6d
inner-shell resonance of singly ionized barium, as the expanding plasma
plume moves across it. The attenuated beam is allowed to fall on a CCD
array where the spatial distribution of the absorption is recorded.
Time-resolved ion velocity and integrated column density maps are
readily extracted from the photoionization images.