LASER INDUCED FLUORESCENCE (LIF) SPECTROSCOPY OF JET COOLED ThO

Knowledge of actinide bonding is essential for nuclear energy and reactor applications, including nuclear waste treatment. Due to its relatively simple electronic structure, thorium oxide (ThO) is an ideal molecule to study actinide bonding. Previous studies have reported visible and near UV band systems that were recorded under high temperature conditions. Spectral congestion significantly complicated the analyses of these data. In the present work we have examined ThO bands under conditions where jet cooling was used to reduce the rotational temperature to approximately 90 K. LIF spectra were recorded over the range 18,000-19,800 \wn. Several new vibronic bands have been characterized. Some extend the data range for known electronic transitions, while others belong to electronic states that have not been reported previously. Analysis of these data and models for the electronically excited states of ThO will be presented