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Title:Infrared Spectra Of (co2)n - (rare Gas)m Trimers And Tetramer, (n,m) = (1,2), (1,3), (2,1)
Author(s):McKellar, A.R.W.
Contributor(s):Moazzen-Ahmadi, Nasser; Pietropolli Charmet, Andrea; Barclay, A.J.
Abstract:\textbf{(\textit{n},\textit{m}) = (1,2).}~~ CO$_2$-Ar$_2$ has previously been studied in the microwave\footnote{Y. Xu, W. J\"{a}ger, and M.C.L. Gerry, \textit{J. Mol. Spectrosc.} \textbf{157}, 132 (1993).} and infrared.\footnote{J.M. Sperhac, M.J. Weida, and D.J. Nesbitt, \textit{J. Chem. Phys.} \textbf{104} 2202 (1996).} Its structure has two Ar atoms occupying equivalent positions around the 'equator' of the CO$_2$, giving $C_{2v}$ symmetry. Here we report observation of analogous infrared spectra of CO$_2$-Ne$_2$ and CO$_2$-Xe$_2$. Meanwhile, for CO$_2$-Ar$_2$ we observe a new $a$-type combination band giving an intermolecular bending frequency of 32.2 \wn. Unlike the fundamental band, the combination band is free of interference from stronger CO$_2$-Ar transitions. Also, we observe CO$_2$-Ar$_2$ in the CO$_2$ (01$^{1}$1) - (01$^{1}$0) hot band region, as well as weak fundamental band spectra of the mixed trimers CO$_2$-Rg-He, with Rg = Ne, Ar, Xe. \textbf{(\textit{n},\textit{m}) = (1,3).}~~ An interesting band near 2345.2 \wn~is assigned to CO$_2$-Xe$_3$, whose structure appears to have $C_s$ symmetry containing a xenon trimer (near equilateral triangle) and a CO$_2$ positioned so that two of the Xe atoms are in equivalent near equatorial positions. \textbf{(\textit{n},\textit{m}) = (2,1).}~~ We have assigned spectra of new trimers, (CO$_2$)$_2$-Rg. The Xe-containing species was noticed first, and this led us to identify weaker spectra with Ar and (even weaker) Ne. Their structures resemble having a CO$_2$ dimer (planar slipped parallel) with the Rg atom located 'above' the dimer plane on (or close to) the dimer symmetry axis, analogous to (CO$_2$)$_2$-CO.\footnote{A.J. Barclay, A.R.W. McKellar, and N. Moazzen-Ahmadi, \textit{Chem. Phys. Lett.} \textbf{677}, 127 (2017).} In the future, it should be possible to assign the various Kr clusters and to optimize each cluster by varying the expansion gas mixtures.
Issue Date:2021-06-25
Publisher:International Symposium on Molecular Spectroscopy
Genre:Conference Paper / Presentation
Date Available in IDEALS:2021-09-24

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