INS studies of solid CO2

Carbon dioxide is arguably the most (in)famous molecule in chemistry. Our interest in CO2 stems from the Fermi resonance between the overtone of the bending mode (2ν3) and the symmetric stretch (ν1). I In a recent TOSCA XPRESS measurement of Tl(NCO), we observed two bands in the region of the symmetric [N=C=O]– stretch, rather than the one expected. We believe that this is the first example of Fermi resonance that has been observed by INS. The possibility that Fermi resonance can be observed by INS is intriguing and we would like to test this by attempting to observe it in the best characterised example, CO2.