Temperature and pressure dependence of the line shape at λ = 763 nm in oxygen concentration detection

Gas line shape is determined by the Voigt profile, which is the convolution of Lorentz and Doppler profiles. The calculation amount in the Voigt profile is much larger than that in the two other profiles, and an approximate Lorentz or Doppler profile is generally used in gas concentration detection via tunable laser absorption spectroscopy. The normalized peak ratio and error function are introduced to compare the approximating effect of the two profiles. The normalized peak ratio value is simulated for Doppler profile and Lorentz profiles over a variable temperature and pressure, respectively. The 10%, 5% and 2.5% error functions for pressure versus temperature are obtained for the two profiles. Oxygen at a wavelength of 760 nm is used to demonstrate the simulation results. The presented method of investigating line shapes can be applied to other gas spectrum lines.