Identification of the (CO2)(2) dimer vibrations in the nu 1, 2 nu(2) region: Anharmonic variational calculations

This paper aims at examination of the (CO2)(2) Spectral absorption profile retrieved from the room temperature CO2 collision-induced absorption (CIA) spectrum in the region of the upsilon (1), 2 upsilon (2), Fermi doublet. Th e assignment Of (CO2)(2) vibrations is discussed, paying due attention to h igh-resolution CARS observations in the regions of and v(low) and v(up). A variational solution of the anharmonic vibrational problem for the (CO2)(2) dimer was obtained using an extended basis set consisting of harmonic and Morse oscillator wave functions. This allowed for a satisfactory descriptio n of the vibrational dimer upsilon (1), 2 upsilon (2) spectrum from first p rinciples. In particular, we have succeeded in proving that the diffuse abs orption band seen in the trough between the major Fermi-coupled CIA bands b elongs to combinations of CO2 bending vibrations in a dimer. (C) 2001 Acade mic Press