were large enough to anticipate the observation of partially resolved rotational structure for the vibronic bands, and they defined the molecule as a near-prolate symmetric top with a Ray's asymmetry parameter of approximately -0.74. In the following we designate the vibrational states with the labels (v1, v2, v3) where v1 is the O-ThF stretch, v2 is the bend and v3 is the OTh-F stretch.