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

Abstract

The B–F bond distance r_g 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 r_g 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 D_J=(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, r_z(B–F), of BF₃ was thus determined from the diffraction and infrared experiments to be 1.311₂±0.001 Å.