Infrared Spectrum of Hydrogen Fluoride: Line Positions and Line Shapes Part II Treatment of Data and Results*

Abstract

The spectrometer and experimental methods described in a companion paper were used to measure the center frequencies of some absorption lines in the HF fundamental and first-overtone bands and to measure the pressure-broadened shapes of some lines in the fundamental. The centers of both bands were calculated, and strongly J-dependent, pressure-induced line center shifts were measured for the fundamental. A method for correcting the measured shape of a spectral line for the effects of instrumental broadening in order to obtain the “true shape” is explained. It was possible to obtain the true shape of lines whose pressure broadened half-width was as small (0.03 cm−1) as several times the Doppler half-width.It was found that the true line shape could be represented quite satisfactorily by a modified form of the Lorentz expression, i.e., α=α0(Δν)2[|ν−ν0|η+(Δν)2]−1. For spectral lines whose half-width at one-half the maximum percent absorptance was less than 2.25 cm−1, η=2 gave good agreement between the true shape and that predicted by the Lorentz expression. If this width was greater than 3 cm−1 then η=1.85 allowed the best fit to the true line shape. No pressure dependence of η could be measured in the range of pressures used (0–5 atm).