Strengths and widths in the first overtone band of hydrogen fluoride

Abstract

The strengths and self-broadened half widths of 18 lines of the first overtone band of hydrogen fluoride have been measured using a direct measurement method. The lines were assumed to have the Lorentz or combination Lorentz-Doppler shape.Matrix elements have been calculated for a dipole moment function of the form [mu](r) = [Sigma]kMk(r-re)k. Best values of M1 and M2 were found to be M1 = 1.51 x 10-10 esu and M2 = -3.74 x 10-3 esu/cm for a rotating Morse oscillator and M1 = 1.52 x 10-10 esu and M2 = -2.15 x 10-3 esu/cm for the rotating anharmonic oscillator.Line widths were calculated using the Anderson theory. The first-order effect of the vibrational quantum number on the half widths has been taken into account, and a comparison with measurements on the pure rotation and fundamental bands has been made. The measurements show good agreement with theory in that the half widths tend to decrease with increasing [Delta]v. Also in agreement with theory, measured values in the P branch are greater than in the R branch for moderate values of |m|. As |m| increases and the shorter range forces become more important, the R-branch widths tend to become greater than the corresponding lines in the P branch.