The vibronndash;phonon sidebands in the Fourierhyphen;transform infrared spectra of the molecular crystal CO2

摘要

FTIR investigations on polycrystalline CO2at various temperatures show Stokes and antihyphen;Stokes sidebands coupled to the vibrational modesv3,v2, andv+/vminus;(Fermi dyad). The latter is infrared forbidden and may be eliminated from spectra of good quality polycrystalline films. The main peaks in the structure of the sidebands may be assigned to phonons from points of highest symmetry in the Brillouin zone. The vibronndash;phonon coupling process is mode specific and driven by electrical anharmonicity in case ofv+andvminus;. For the infrared allowed fundamentals, and especially at the Ggr; point, the coupling process is also driven by mechanical anharmonicity. The dispersion of these internal modes atk=0 influences the coupled phonons and thus the one phonon density of states is correctly mirrored by thev+andvminus;sidebands only.