Dissociation Energies of Group IIIA Monofluorides—The Possibility of Potential Maxima in Their Excited Π States

Abstract

The dissociation energies D₀″ have been measured for GaF, InF, and TlF using high‐temperature mass‐spectrometric techniques. These results, along with those from previous studies, yield D₀″=180±3, 159±3, 138±3.5, 121±3.5, and 101±3.5 kcal/mole for BF, AlF, GaF, InF, and TlF, respectively. Comparison of D₀″ thus obtained with that derived from Birge—Sponer extrapolation of the A ¹Π state indicates that for all these molecules the spectroscopically derived dissociation energies are higher than the thermochemical values. It is suggested that the difference may be due to a potential maximum in the A ¹Π states BF, AlF, GaF, and InF. A maximum is also suggested for the a ³Π₁ state of TlF. The appearance potentials of these monofluorides were measured and were found to be 11.5±0.4, 9.5±0.5, 10.6±0.4, 9.6±0.5, and 11.2±0.5 eV for BF⁺, AlF⁺, GaF⁺, InF⁺, and TlF⁺, respectively. The dissociation energies and the appearance potentials are briefly discussed in terms of the molecular states of the respective molecules.