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Transition metals and their oxides are relevant for fields like materials science or biochemistry, and have manifold industrial applications. They can serve as catalysts for water activation as an early step in the formation of molecular hydrogen [1]. Tantalum is a third row transition metal and in the past a variety of studies were performed on reactions involving water [2]. In order to be able to study these properties the systems are often simplified by going to small gas phase clusters and the method of argon tagging in combination with infrared spectroscopy is used to determine the structures formed in the reactions. However, using the intracavity free electron laser FELICE at the HFML-FELIX institute allows for the study of bare clusters by infrared multiple photon dissociation (IRMPD) without having to rely on an additional tag. In the present study, water activation on TaO$_2^+$ cations has been studied in the region of 350 cm$^{-1}$ - 1600 cm$^{-1}$. Additionally, quantum chemical calculations were performed using chemical reasonable structures as a starting point. Comparing the experimental spectra with the theoretical frequencies and intensities leads to the conclusion that for both the singly and doubly hydrated cations the hydroxide species are formed. The calculated potential energy surfaces, where TaO(OH)$_2^+$ and Ta(OH)$_4^+$ are the lowest lying minima, are consistent with this assignment. All results are in good agreement with the work of Wang et al. [3], who performed IRMPD of the O-H stretching modes.
