ABSOLUTE ROVIBRATIONAL INTENSITIES OF (CO2)-C-12-O-16 ABSORPTION-BANDS IN THE 3090-3850 CM(-1) SPECTRAL REGION

A multispectrum nonlinear least-squares fitting technique has been use d to determine the absolute intensities for approximately 1500 spectra l lines in 36 vibration-rotation bands of (CO2)-C-12-O-16 between 3090 and 3850 cm(-1). A total of six absorption spectra of a high-purity ( 99.995% minimum) natural sample of carbon dioxide were used in the ana lysis. The spectral data (0.01 cm(-1) resolution) were recorded at roo m temperature and low pressure(1 to 10 Torr) using the McMath-Pierce F ourier transform spectrometer of the National Solar Observatory (NSO) on Kitt Peak. The absorption path lengths for these spectra varied bet ween 24.86 and 385.76 m. The first experimental determination of the i ntensity of the theoretically predicted 2 nu(2)(2) + nu(3) ''forbidden '' band has been made. The measured line intensities obtained for each band have been analyzed to determine the vibrational band intensity, S-nu, in cm(-1)/(molecule cm(-2)) at 296 K, square of the rotationless transition dipole moment \R\(2) in Debye(2), as well as the nonrigid rotor coefficients. The results are compared to the values listed in t he 1996 HITRAN database which are obtained using the direct numerical diagonalization (DND) technique as well as to other published values w here available. (C) 1998 Elsevier Science Ltd. All rights reserved.