Infrared and Raman studies of pressure effects on the vibrational modes of solid CO2

Infrared and Raman studies have been made on the librational and internal modes of solid CO2 in the pressure range of 6 to 120 kbar at ambient temperature. The Fermi resonance has been analyzed in detail. Both of the stretching modes stiffen with pressure while the bending mode softens with pressure. The magnitude of the Fermi interaction parameter W decreases somewhat with pressure. A simple model using gas phase anharmonic constants predicts much of the observed behavior.