N 2, O 2, H 2, Ar and He broadening in the ν 1 band of NH 3

Abstract

N 2-, O 2-, H 2-, Ar- and He-broadening coefficients and pressure shifts have been measured for Q- and R-branch transitions in the ν 1 fundamental band of ammonia using a difference-frequency laser spectrometer. The J- K dependence of the broadening coefficients is much smaller than previously observed for self broadening of NH 3. Semiclassical line broadening calculations for N 2 broadening are in reasonable quantitative agreement with the data, but they also exaggerate the J- K dependence. Dicke narrowing is observed as strong deviations from Voigt profiles at intermediate pressures and provides estimates for optical diffusion constants which correlate well with the mass diffusion constants for NH 3 in the various buffer gases.