The perpendicular vibrations of boron trifluoride

Abstract

An analysis of the ν 3 band of 10BF 3 as observed by Dreska, Rao, and Jones has been performed by comparing the observed high resolution contour with that obtained by computation for different sets of molecular parameters. The contour was found to be extremely sensitive to small changes in the parameters, which therefore were determined to high accuracy. An essentially perfect fit was obtained with B″ = 0.3527, B′ = 0.3515, A″ = 0.17635, A′ = 0.17575 cm −1, ζ 3 = +0.81 ± 0.01. In the same way, the ν 3 band of 11BF 3 was best analyzed using the same rotational constants but with ζ 3( 11 B) = +0.795 ± 0.01 , and the ν 4 band contour of 11BF 3 as observed by Levin and Abramowitz was best reproduced using the parameters B = B′ = 0.3527, A″ = A′ = 0.17635 cm −1, ζ 4 = −0.80 ± 0.02. The zeta constants obtained are consistent with each other and with two independent estimates of the isotope frequency shift on ν 4. The force field for the BF 3 molecule is thus determined to within narrow limits.