Pressure broadening and shift coefficients in the ν1 and ν3 bands of NH3. (November 2018) - Maaroufi, N.
Highlights: Self-broadening and self-shift coefficients of 510 transitions in the ν1 and ν3 bands of NH3 have been measured at T = 295 K. The first-order Rosenkranz profile accounting for line-mixing effect was adopted to fit the Fourier Transform spectra. Line-mixing coefficients of 220 lines in the ν1 and ν3 bands of NH3 have been retrieved. The measured shift coefficients are bipolar. Line-mixing effects contribute to the observed shift with a quadratic dependence in pressure. Abstract: Self-broadening and self-shift coefficients have been measured in the ν1 and ν3 bands of NH3 at room temperature for about 510 ro-vibrational lines with rotational quantum numbers 1 ≤ J ≤ 11 . The measurements have been made in numerous branches located in the spectral range from 3050 to 3600 cm −1 using a high-resolution Fourier transform spectrometer. The data have been retrieved using a non-linear least squares multi-pressure fitting procedure of the first-order Rosenkranz profile to eight spectra of NH3 . Analysis of the overlapped lines has allowed the measurement of line-mixing parameters for about 200 transitions. The results of pressure broadening coefficients obtained with and without accounting for line-mixing effect have been analyzed as a function of the branches. On average, the accuracies of self-broadening coefficients are estimated to be better than 4%. Those of self-shift and line-mixing are estimated to be about 11% and 17% respectively. About half of the lines have negative shift coefficients with numerous opposite signs for the symmetric and asymmetric doublet components. This work has also shown that line-mixing effects can contribute to the observed shift with a quadratic dependence in pressure. The whole set of results is given as supplementary material for use in spectroscopic databases.