Note that the simulation included an excited state spin-rotation parameter of 𝜖 !! " =1.9 cm -1 and a saturation parameter of 30 (not surprising given the large oscillator strength of 3 2 A²-𝑋 ) 1 2 A' transition). The rotational temperature of the simulation was 30 K. Further computational studies found that an increase of the size of the basis sets reduces the computed O-Th-F angle of the 3 2 A² state. The EOM-CCSD/QZ calculation gives an angle of 118.0º, to be compared with the TZ value of 119.0º in Table . The basis-set-limit value is expected to be around 117º. This supports the structure obtained in the fitting with an angle of 116.5º. This comparison underlies the value of the by MRCI-SO calculations (Table in the supplemental information). At the crossing point the wavefunctions are almost equal mixtures of the 4 2 A' and 3 2 A² basis states. This explains how the transfer between states of A' and A² symmetry can occur under collision-free conditions. It is of interest for future computational work to include spin-orbit coupling among the vibronic states of the 4A' and 3 2 A² electronic states to improve the simulation.