NH₃ line broadening coefficients and intensities measurement and impurities determination in emerging applications:...

A mid-infrared quantum cascade laser (Mid-IR QCL) coupled with a Single Pass Cell and a Multi Pass Cell, was utilized to measure ammonia (NH₃) absorption spectroscopic parameters and determine NH₃ impurities toward three emerging applications. We for the first time measured the pressure broadening coefficients perturbed by Air, O₂, N₂, He, CO₂, CH₄, and H₂ and the line intensities of six NH₃ transition lines near 1084.6 cm^-1. The measured NH₃-He, NH₃-Air, and NH₃-CO₂ broadening coefficients align with HITRAN database, while NH₃-H₂ coefficients exhibit a maximum discrepancy of 46 %. Deviations between the measured line intensities and HITRAN database are minimal. Nevertheless, the uncertainties of line intensities have been significantly reduced from 20 % in HITRAN to below 3 %. The newly measured line parameters are utilized to address NH₃ impurity requirements outlined in CCUS (ISO 27913:2016), Biomethane (EN 16723:2016), and H₂ (ISO 14687:2019) standards. Based on the concept of optical gas standard (OGS), the NH₃ impurity detection requirements in all three standards have been fulfilled with an uncertainty of 1.35 %. The precision of the NH₃-OGS is 800 part per trillion (ppt) with an integration time of 100 s. The repeatability of the NH₃-OGS is 130 ppt for a continuous measurement time of 48 min. Notably, the NH₃-OGS effectively addresses the highly nonlinear adsorption-desorption dynamics, underscoring the potential of OGS as a calibration-free and SI-traceable metrological gas analysis instrument.