Pressure broadening and cross relaxation of ammonia perturbed by hydrogen and helium: Implications on intermolecular potentials and discussion of rotational effects

Abstract

The study of the absorption line profiles in the infrared region (6-7 pm), by means of a diode laser spectrometer and a Ff spectrometer in ammonia diluted in He and H2 at room temperature, allowed us to determine pressure broadening cross section and the intradoublet inelastic rate (due to molecular inversion).

H2-Broadening Coefficients in the ν4 Band of NH3

“…We estimate indeed that, the conclusion obtained in Ref. (8) of a strong vibrational effect on the NH 3 In this work, we present measurements of H 2 pressure broadening coefficients at room temperature for 66 lines in the P P and R P branches of the ν 4 perpendicular band of NH 3 in the region between 1470 and 1600 cm −1 . These broadening coefficients have been calculated on the basis of the semiclassical model developed in Ref.…”

“…Ground state transitions were studied by Aroui et al (2) and then by Brown and Peterson (3) with a Fourier transform spectrometer; the ν 1 band was studied by Pine et al (4) using a difference-frequency laser spectrometer; and the ν 2 band was studied by Baldacchini et al (5), Margolis and Poynter (6), and Varanasi and Gopalan (7) with a tunable diode laser (TDL) spectrometer. In the ν 4 band only three lines were measured by Broquier et al (8) using a TDL spectrometer.…”

Line Broadening and Mixing in NH3 Inversion Doublets Perturbed by NH3, He, Ar, and H2

“…On the other hand, line-mixing effects in ammonia have, to our knowledge, received little interest (15,(23)(24)(25), although this process was pointed out three decades ago (26).…”

“…(10,11) and those cited therein). Finally, more empirical fitting laws (1,12) or semiclassical approaches have made possible the analysis of line-coupling for nonlinear species whose spectra include large numbers of transitions (13)(14)(15).…”

Pressure-induced line mixing in the ν4 band of NH3 perturbed by O2 and self-perturbed

“…For Ammonia, several studies have been focused on line-mixing effects at low pressures [11][12][13][14][15][16][17][18][19][20].…”