Spectral Intensity and Lineshape Measurements in the First Overtone Band of HF Using Tunable Diode Lasers

Abstract

High-resolution absorption lineshapes for theP(3) andP(6) transitions of the first overtone (v= 2–0) band of HF at 296 K have been measured using a pair of distributed feedback diode lasers operating near 1.31 and 1.34 μm, respectively. Spectral line intensities and self-broadening parameters were determined by fitting the measured spectra with Voigt, Galatry, and Rautian lineshape models. Voigt profiles fit the low-pressure (<10 Torr) spectra of theP(3) transition reasonably well due to the relatively strong collisional broadening effect. Lineshape measurements of theP(6) transition (for pressures ranging from 5 to 60 Torr) show significant variation from the Voigt lineshape model due to velocity-changing collisions that effectively reduce the Doppler component of the spectral line. Lineshape models that include motional (Dicke) narrowing effects, Galatry (soft collision) and Rautian (hard collision) profiles yield significant improvements in the spectral lineshape fits compared with Voigt profiles. The collisional broadening coefficient (γ) of theP(6) transition obtained from a Voigt fit is ∼4% lower than those found with either Galatry or Rautian profile fits. The measured intensities and self-broadening coefficients are compared with values in the HITRAN database and previous measurements.