The infrared matrix isolation spectra of carbon dioxide. II. Argon matrices: the CO₂ monomer bands

Abstract

Evidence is presented that the cause of the doubling of the infrared bands of CO₂ in an argon lattice is the presence of two types of acceptable sites for the CO₂ molecule. The nature of these sites is discussed; it is concluded that the sites are double substitutional sites, in which a CO₂ molecule occupies the place of two adjacent argon atoms, and single substitution sites, in which the CO₂ molecule occupies the place of a single argon atom. A CO₂ molecule in a double substitutional site is a more stable situation than a CO₂ molecule in a single substitutional site: the former gives a higher v₃ and lower v₂ frequency than the latter.