Laboratory studies of the newly discovered infrared band at 4705.2/cm (2.1253 microns) in the spectrum of Io - The tentative identification of CO2

The present evaluation of results from over 120 laboratory experiments relevant to the Trafton et al. (1991) discovery of a 2.1253-micron line in the spectrum of Io demonstrates that this band is produced by neither overtones nor combinations of the fundamental bands of molecules already noted on Io. Since the band's frequency is close to the first overtone of the nu(3) asymmetric stretching mode of CO2, attention is given this molecule's behavior under Io conditions. While pure solid CO2, and CO2 intimately mixed in a matrix of solid SO2 and H2S, generate bands of similar widths, these fall at frequencies lower than the Io band. Attention is given to the possible identification of the Io band with CO2 multimers of 'clusters' on Io.