Experimental and theoretical study of line mixing in NH3 spectra. I. Scaling analysis of parallel bands perturbed by He

Abstract

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Self- and foreign-gas-broadened lineshapes in the ν1 band of NH3

“…Previous semiclassical theoretical models qualitatively describe the self-broadenings [1] but strongly exaggerate the J À K dependence for the non-polar buffers [2,28,34]. Empirical polynomial models [15,16] based only on J and K also have difficulty representing self-broadening at low J, and the Q-branch broadenings for non-polar buffer gases.…”

“…The self shifts are one to two orders of magnitude smaller than the self-broadenings, and, where determinable, their signs depend on the inversion symmetry. Inclusion of line mixing in first order permits us to extend the fits to higher pressure, but a full relaxation matrix inversion [6,7,19,34] may be required at even higher pressure. The opposite signs and nearly equal magnitudes of the f m for the m 1 and m 3 s À a tunneling partners are another indication of the dominant coupling for self-broadening.…”

“…However, for non-polar buffer gases, the effect is generally weaker [29,[31][32][33]. High-pressure studies of NH 3 in a variety of buffers [34] exhibit strong line mixing in the m 1 and m 2 Q branches and even between J manifolds in the P and R branches, and demonstrate the need to use a full relaxation matrix inversion procedure to adequately describe the absorption contours.…”

Line shift and mixing in the ν4 and 2ν2 band of NH3 perturbed by H2 and Ar

“…Recently, Hadded et al [13] have studied line mixing of 15 inversion doublets of NH 3 perturbed by He, Ar, and H 2 . More recently, these authors [14,15] have measured line mixing effects in the m 1 and m 2 bands of NH 3 at high pressure. They have demonstrated the necessity of take into account line mixing for the treatment of inversion-rotation spectra of NH 3 .…”

Shifting and line mixing parameters in the ν4 band of NH3 perturbed by CO2 and He: Experimental results and theoretical calculations

“…In other studies, it was shown that line mixing could greatly influence the values of the molecular parameters obtained during fitting processes with assumed line shapes. In fact, line mixing was also taken into accounted in several studies for the m 1 , m 2 , and m 4 bands of NH 3 perturbed by He, Ar and H 2 [5][6][7].…”