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.

An ab initio study of the electronic structure of BF and BF+

“…Correcting for CV effects, we find r e = 1.218 − δr e = 1.218 − 0.003 = 1.215 Å in perfect agreement with the experimental value of r e = 1.2149 Å (see Table I). The two atoms are slightly bound by 12.2(9.0) kcal/mol at the valence MRCI(+Q)/A6ζ level as compared to an experimental value being 7.5 kcal/mol, 7,16,57 and a large barrier of 27.7 kcal/mol which prevents its dissociation. The equilibrium CFs…”

“…Unfortunately, they could not deduce any information on the dissociation energy (D) of the X-state, although a value of 7.81 ± 0.13 eV had already been given based on previous thermochemical data. 16 It is worth noticing at this point that a D 0 value larger by 5 kcal/mol based on a Birge-Sponer extrapolation of the vibrational levels of the A 1 state had been already reported. 17 This 5 kcal/mol difference was attributed to a maximum in the potential curve of that A 1 state, considering the systematic and uniform discrepancies found in a series of group IIIA monofluorides.…”

“…17 This 5 kcal/mol difference was attributed to a maximum in the potential curve of that A 1 state, considering the systematic and uniform discrepancies found in a series of group IIIA monofluorides. 16 In a microwave study, Lovas and Johnson 18 observed direct rotational transitions in the ground vibrational state of 10,11 BF leading to improved ground state constants. A dipole moment value of 0.5 ± 0.2 D was also reported for the first (and last) time.…”

Structural parameters of the ground states of the quasi‐stable diatomic anions CO−, BF−, and BCl− as obtained by conventional Ab Initio methods

“…The BF molecule is a (formally) triply bonded closed shell system, isoelectronic to CO, and strongly bound; its experimental bond length and binding energy are r e = 1.26712 Å and D 0 = 180 ± 3 kcal/mol (=7.806 ± 0.130 eV), respectively; see also Ref. .…”

Theoretical study with dipole moment calculation of new electronic states of the molecule BF

“…Between 1957 and 1985, many electronic states have been investigated by using different experimental techniques [1][2][3][4][5][6][7][8][9][10]. Between 1988 and 2011, 22 singlet and triplet electronic states have been studied theoretically .…”