Overtone Raman spectrum and molecular polarizability surface of CO 2

9 pags., 2 figs., 1 tab.The Q branches of the Raman bands associated to the 2ν1: 4ν2 0:ν1\ 2ν2 0 Fermi resonance of 12C 16O2 have been observed in the gas phase at 2543, 2671, and 2797 cm-1 and, in addition, at 2514 cm-1, one hot band from their first excited vibrational state is seen. From the analysis of their cross sections, jointly with those of the main Fermi diad, ν1:2ν2 0 and its hot bands, an improved description of the molecular polarizability surface has been achieved. The following derivatives of the mean polarizability have been obtained: ∂ᾱ/∂q1=12.43 ×10-42 CV-1 m2; ∂2ᾱ/∂q 2σ 2=2.81×10-42 CV-1 m2 (σ=a,b); ∂2ᾱ/∂q 1 2=0.45×10-42 CV-1 m 2; ∂2ᾱ/∂q3 2=0.67 or 0.15×10-42 CV-1 m2; ∂3alpha;̄/∂q1∂q 2σ 2=-0.06×10-42 CV-1 m2, in terms of the dimensionless normal coordinates, and ∂ᾱ/∂S1=3.15×10-30 CV -1 m; ∂ᾱ/∂S2σ 2=0.36×10-20 CV-1; ∂ 2ᾱ/∂S1 2=2.9×10 -20 CV-1; ∂2ᾱ/∂S 3 2=2.0 or 0.5×10-20 CV-1; ∂3ᾱ/∂S1∂S 2σ 2=-1.7×10-10 CV-1 m-1, in terms of the symmetry coordinates. The thermal dependence of the mean polarizability is discussed in terms of these quantities. © 1995 American Institute of Physics.The Direccio´n General de Investigacion Cientıfica y Tecnica (DGICYT), of Spain, is acknowledged for financial support