The infrared spectrum of clustered carbon dioxide: An interpretation via bulk optical constants

The diffusive trapping technique, in which a condensable vapor is injected into a cold buffer gas, has been used to produce clusters of carbon dioxide and nitrous oxide containing approximately 109 molecules. The infrared spectrum of these clusters was recorded using a Fourier-transform spectrometer. Major features of the carbon dioxide spectrum were reproduced by solving Maxwell’s equations for light interacting with a sphere having a complex dielectric response equal to that of solid carbon dioxide. The calculation also allowed for an estimation of the cluster size. Additional features of the spectrum suggest the presence of edges and corners on the clusters.