The experimental results presented in this paper shed light on some of the fundamental bonding characteristics of NbH and TaH. Six bands of niobium hydride and five weak bands of tantalum hydride were observed for the first time using laser excitation spectroscopy. The rotational assignments of observed bands were confirmed using dispersed fluorescence experiments for NbH and by checking the internal consistency of a global least squares fit for the weaker bands of TaH. For TaH, we were able to determine the term energies and molecular constants of each of its observed states to a high degree of accuracy by doing a combined global fit of the newly observed bands along with the previously known ones. For NbH, our preliminary experimental values compare well with computational predictions by Koseki et al. (2004). Upper states of both NbH and TaH show indications of perturbations with dark states. Further spectroscopy of NbH at higher wavelengths has to be carried out to characterize more electronic states.

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