Line intensity measurements in 14N216O and their treatment using the effective dipole moment approach

This work continues a series of publications devoted to the application of the effective operator approach to the vibrational-rotational treatment of linear triatomic molecules, aiming at the analysis and prediction of their infrared spectra. In that frame work, we have started a large-scale work aiming at the global description of line intensities of cold and hot bands of N-14(2) O-16 in its ground electronic state in the spectral range above 3600 cm(-1). In (N2O)-N-14-O-16, vibrational interacting levels group in polyads as a result of the relation 2 omega (1) approximate to 4 omega (2) approximate to omega (3) existing between the harmonic frequencies. The polyads are identified by the so-called polyad number P = 2V(1) + V-2 + 4V(3). The work described in the present paper concerns bands associated with transitions corresponding to DeltaP = 7, 8, and 9. The absorption spectra of N2O at room temperature have been recorded at a resolution of 0.007 cm(-1) in the range from 4300 to 5200 cm(-1) using a Bruker IFS120HR Fourier transform spectrometer. Sample pressure/absorption path length products ranging from 7 to 1753 mbar x in have been used. More than 3000 absolute line intensities have been measured in 66 different bands belonging to the AP = 7, 8, and 9 series. Dicke narrowing has been observed in the high-pressure spectra. Using wavefunctions previously determined from a global fit of an effective Hamiltonian to about 18,000 line positions (S. A. Tashkun, V. I. Perevalov, and J.-L. Teffo to be published), the experimental intensities measured in this work and by R. A. Toth (J. Mol. Spectrosc. 197, 158-187 (1999)) were fitted to 47 parameters of a corresponding effective dipole moment, with residuals very close to the experimental uncertainty. Examples are given showing that the modeling reproduces intensities of perturbed lines well. (C) 2001 Academic Press.