Knowledge Bank

Measurements of line intensities in the fundamental band of HF have been extended from $m=-10$ to $m=+12$. The rotational correction factors $Fu1$(m) have been calculated and the experimental curve of $F01$(m) versus m has been compared with that predicted by Herman and Wallace. The experimental curve drops below predicted values in both wings of the band, though not so abruptly in the P-branch as in the R-branch. An attempt has been made by the method of Herman and Rubin to fit the experimental curve taking both a linear and a quadratic expression for the dipole moment expansion. It is possible with the linear dipole moment expression to fit the experimental curve through the center of the band, but not in the wings. No better fit is obtained with a quadratic expression for the dipole moment. Another approach seems desirable that will explicitly incorporate the effect of the large vibration-rotation term present in the experimentally determined general potential function for the molecule. Waggoner and Shaffer have applied the contact transformation method to the effect of vibration-rotation interaction on the line intensities of the linear symmetric molecule. An adaptation of this approach is being applied to HF to take explicit account of the large distortions in this light molecule.