  We describe a system to transport and identify barium ions produced in liquid
xenon, as part of R&D towards the second phase of a double beta decay
experiment, nEXO. The goal is to identify the Ba ion resulting from an
extremely rare nuclear decay of the isotope $^{136}$Xe, hence providing a
confirmation of the occurrence of the decay. This is achieved through Resonance
Ionization Spectroscopy (RIS). In the test setup described here, Ba ions can be
produced in liquid xenon or vacuum and collected on a clean substrate. This
substrate is then removed to an analysis chamber under vacuum, where
laser-induced thermal desorption and RIS are used with time-of-flight (TOF)
mass spectroscopy for positive identification of the barium decay product.
