B–F Bond Distance of Boron Trifluoride Determined by Gas Electron Diffraction

The B–F bond distance rg of BF3 was determined by gas electron diffraction to be 1.3133±0.0010 Å. The corresponding rotational constant B0 was calculated to be 0.3449±0.0006 cm−1 from the rg distance by the use of the theory of rotation—vibration interaction. This value was consistent with the rotational fine structure of the v2 infrared band reported by Nielsen, when slight changes in his J assignments were made. The reanalysis of his spectral data led to B0=0.3449 cm−1 and DJ=(4.1±0.4)×10−7 cm−1. The latter constant was in good agreement with the theoretical estimate, 4.13×10−7 cm−1. The zero-point average distance, rz(B–F), of BF3 was thus determined from the diffraction and infrared experiments to be 1.3112±0.001 Å.