Infrared Spectra Of (co2)n - (rare Gas)m Trimers And Tetramer, (n,m) = (1,2), (1,3), (2,1)

extbf{( extit{n}, extit{m}) = (1,2).}~~ CO2-Ar2 has previously been studied in the microwaveootnote{Y. Xu, W. J"{a}ger, and M.C.L. Gerry, extit{J. Mol. Spectrosc.} extbf{157}, 132 (1993).} and infrared.ootnote{J.M. Sperhac, M.J. Weida, and D.J. Nesbitt, extit{J. Chem. Phys.} extbf{104} 2202 (1996).} Its structure has two Ar atoms occupying equivalent positions around the 'equator' of the CO2, giving C2v symmetry. Here we report observation of analogous infrared spectra of CO2-Ne2 and CO2-Xe2. Meanwhile, for CO2-Ar2 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 CO2-Ar transitions. Also, we observe CO2-Ar2 in the CO2 (0111) - (0110) hot band region, as well as weak fundamental band spectra of the mixed trimers CO2-Rg-He, with Rg = Ne, Ar, Xe. extbf{( extit{n}, extit{m}) = (1,3).}~~ An interesting band near 2345.2 wn~is assigned to CO2-Xe3, whose structure appears to have Cs symmetry containing a xenon trimer (near equilateral triangle) and a CO2 positioned so that two of the Xe atoms are in equivalent near equatorial positions. extbf{( extit{n}, extit{m}) = (2,1).}~~ We have assigned spectra of new trimers, (CO2)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 CO2 dimer (planar slipped parallel) with the Rg atom located 'above' the dimer plane on (or close to) the dimer symmetry axis, analogous to (CO2)2-CO.ootnote{A.J. Barclay, A.R.W. McKellar, and N. Moazzen-Ahmadi, extit{Chem. Phys. Lett.} extbf{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.