Reassessment of ammonia self- and air-broadened half-widths for the HITRAN database

Accurate NH₃ pressure-broadening parameters are required for reliable line-by-line simulations in a multitude of applications including atmospheric sensing, combustion diagnostics, and planetary/exoplanet applications. Current HITRAN NH₃ self- and air-broadened half-widths are largely based on the Nemtchinov rotational correlation and subsequent database rules that clamp or assign default values outside the validated range. This treatment avoids nonphysical extrapolation but suppresses the measured rotational dependence, especially for high- J ′′ transitions. In this work, published laboratory measurements of NH₃ self- and air-broadened Lorentz half-widths were compiled and reassessed to develop updated empirical correlations for HITRAN. The collected dataset contains 1317 self-broadened and 1231 air-broadened half-widths at, or reduced to, 296 K, spanning multiple vibrational bands, branches, and rotational quantum numbers. The analysis confirms that the dominant dependence of the linewidths is rotational, rather than branch-, band-, or vibration-inversion-specific. Constrained third-degree polynomial correlations were fitted for γ_self and γ_air as functions of the branch-dependent rotational index m and K ′′. The regression was weighted by reported measurement uncertainties and constrained to remain positive over the intended HITRAN rotational domain. The new fit reduces the air-broadening mean absolute percentage error (MAPE) from 10.95% for HITRAN2024 to 6.80%. For self broadening, the MAPE decreases from 23.61% for HITRAN2024 to 10.89%. Spectrum-level comparisons with PNNL-database spectra and pure-NH₃ measurements show that the updated coefficients improve simulated absorption profiles for both foreign-gas and self-broadened conditions. These results provide a physically constrained, database-ready replacement for the current HITRAN NH₃ self- and air-broadening treatment.