STRUCTURES OF $N_{2}O$ DIMERS AND CLUSTERS FROM FTIR SPECTRA OF $N_{2}O / Ar$ SUPERSONIC EXPANSIONS
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Date
1987
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Ohio State University
Abstract
In very dilute expansions, 0.2\% $N_{2}O$ in Ar, dimer bonds of 1282 and $2228 cm^{-1}$ were observed corresponding to the $\nu_{1}$ and $\nu_{2}$ stretches of the monomer. As an example, the $\nu_{1}$ region spectra are shown in the figure for various dilutions. In the dimer, the NO stretch frequency is reduced and the NN stretch frequency is increased consistent with a staggered paralled configuration with the O atoms towards the centre. The dimer bond at $2228 cm^{-1}$ is shifted $+5 cm^{-1}$ while the $Ar-N_{2}O$ complex bond origin shift is only $+0.1509 cm^{-1 1}$ ``Cluster bands'' (we have no means of determining the cluster size) corresponding to 6 bonds of the monomer were readily observed in rich mixtures. $-Q-100\% N_{2}O$ at 1165, 1296, 2246, 2467, 2578, and $3506 cm^{-1}$. For all three bonds $2\nu_{2}. \nu_{1}$, and $\nu_{3}$ observed here and in the crystal, the cluster shift is larger and in the same direction. In $SF_{**}-Ar clusters^{3}$, a sharp peak appeared in the linewidth against size for clusters around $n=14$ which suggested a phase change. Such a peak was not observed here. Rother, the linewidths decreased monotonically with richer mixtures (larger clusters) suggesting a structure getting more and more rigid, as in the high pressure range of the $SF_{**}$ work. $(N_{2}O)_{2}$ linewidths were in the range $2-3 cm^{-1}$. Helium as a carrier gas gave the same results although clustering was more pronounced in Argon.
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1) J.Hodge, G.D.Hayman, T.R.Dyke and B.R.Howard, J.Chem.Soc., Faraday Trans. 2.82,1137 (1986). 2) A.Anderson and T.S.Sun, Chem.Phys.Letters.8.537(1971). 3) D.Elchenouer and R.J.LeRoy, Phys.Rev.Letters,57,2920 (1986).
Author Institution: Laser Chemistry Group, National Research Council
Author Institution: Laser Chemistry Group, National Research Council