Measurement research of line intensity and self-broadening coefficient for NH₃ spectra in 4296–4302 cm^–1

Abstract

Spectral parameters of NH₃ in a range of 4296–4302 cm^–1 in the HITRAN database are different from the actual situation as they are derived from theoretical calculations. In order to correct the spectral parameters of NH₃ in this range in HITRAN, tunable diode laser absorption spectroscopy (TDLAS) technology and metrological theory are used to measure the absorption spectrum high-purity NH₃ in the range of 4296–4302 cm^–1 at 2–10 Torr. The line intensity and self-broadening coefficient of the main absorption line of NH₃ in this band are retrieved and their uncertainty are calculated by comprehensively considering main factors including pressure, temperature, optical path of gas cell, wavenumber and line shape fitting. The discrepancies between our measured line intensities and latest peer-measured results are within 20%. The biases between our self-broadening coefficients and the ones in HITRAN2020 are within 14%. Their uncertainties are in a range of the 0.63–2.7% and 0.77–5.4%, respectively, which are smaller than the uncertainty range of 10–20% in the HITRAN database. Some of the measured spectral parameters are not recorded in HITRAN. The experimental results in this work are of significant reference in supplementing and correcting the HITRAN spectral parameters of NH₃ in the range of 4296–4302 cm^–1.