Isotope effects on vibrational excitons in carbon dioxide particles

The vibrational exciton approach is used to answer a long-standing question concerning the infrared spectra of CO2 particles: What causes the characteristic structure of the infrared absorption bands? The CO2 particles which are generated in a collisional cooling cell at 78 K consist of many thousands of molecules. Isotopically pure (12CO2 or 13CO2) particles as well as isotopically mixed (12CO2/13CO2) particles are investigated. Combining the experimental observations with exciton calculations, the band structure in the infrared spectra can be traced back to the shape of the particles.