Signal-enhanced DOAS based on the secondary diffraction spectrum and its application in sulfur dioxide measurement.

In this study, we demonstrate a differential absorption-enhanced method based on secondary diffraction spectra and apply it to the detection of sulfur dioxide based on differential optical absorption spectroscopy (DOAS). An effective approach for extracting the secondary diffraction spectrum is proposed. The absorption spectrum of sulfur dioxide achieved by secondary diffraction was confirmed to match that of primary diffraction in the vacuum ultraviolet region. The enhancement in differential absorption due to the improvement in resolving power was observed. Sulfur dioxide was calibrated and determined based on the primary and secondary diffraction spectra, respectively. When measuring sulfur dioxide concentrations, detection sensitivity and limit of detection (LoD) achieved 10-fold and two-fold improvements, respectively. This study provides a novel, to our knowledge, method for enhancing measurements based on DOAS.