分类: 光学 >> 量子光学 提交时间: 2023-02-19
摘要: Applicability and accuracy of traditional scanned-wavelength direct absorption spectroscopy (SDAS) diagnostic method is largely affected by combustion state such as temperature and pressure. To resolve this problem, an innovative baseline-free scanned-wavelength direct absorption spectroscopy (BF-SDAS) method is proposed in this work. This method does not need the zero-absorption regions for baseline fitting and can exclude the influence of baseline fitting error on the final result. It is especially suitable for the cases when the scanning range is too narrow or the absorption linewidth is too large to acquire the baseline. In this paper, the BF-SDAS is first derived and theoretically analyzed based on the Fourier analysis, and then the accuracy of this method is validated by measuring the concentration of H2O molecules in a static gas absorption cell at room temperature.
分类: 光学 >> 量子光学 提交时间: 2023-02-19
摘要: This paper proposes a novel and rapid calibration-free wavelength modulation spectroscopy algorithm based on even-order harmonics. The proposed algorithm, analytically deduced from Voigt line-shape function, only involves simple algebraic operations to describe the actual gas absorption spectra, thus eliminating the time-consuming simulations and line-shape fitting procedures adopted in traditional algorithms. Instead of acquiring the entirely scanned absorption line-shape, the proposed technique only requires extraction of the peak values of the harmonics. This characteristic significantly benefits gas diagnosis at elevated pressure and/or temperature, in which the entirely scanned absorption is very difficult to be obtained due to the broadened line-shapes. The proposed algorithm is validated by both numerical simulation and condition-controlled experiment, indicating millisecond-level calculation of gas parameters with the relative error less than 4% in the experiments.
分类: 光学 >> 量子光学 提交时间: 2023-02-19
摘要: A simple approximation scheme to describe the width of the Voigt profile as a function of the relative contributions of Gaussian and Lorentzian broadening is presented. The proposed approximation scheme is highly accurate and provides accuracy better than 10^-17 for arbitrary aLaG ratios. In particular, the accuracy reaches an astonishing 10^-34 (quadruple precision) in the domain aLaG less than 0.2371 and aLaG greater than 33.8786.