Searching for the Mass of the Neutrino (Spectroscopy of Ba+ ions in Liquid $^{136}$Xe)

The goal of the Enriched Xenon Observatory (EXO) collaboration is to detect neutrino-less double beta decay using a ton size liquid $^{136}$Xenon detector with zero background. Such detection can only be achieved if the daughter $^{136}$Ba$^{+}$ ion that is present at decay site is tagged. The EXO collaboration is working towards several techniques to tag the Ba$^{+}$ ion. In-situ laser tagging of Ba$^{+}$ ions in a liquid xenon test apparatus is being developed at Colorado State University (CSU). Ba$^{+}$ ions are implanted in the liquid xenon by ablating a barium sample with a 1064nm Nd-YAG pulsed laser. In-situ laser tagging can only be accomplished if the spectroscopy of Ba$^{+}$ ions in liquid xenon is understood. This work's goal is to confirm the spectra of Ba+ ions in liquid xenon. The most recent results of the experiments at CSU will be presented.