Positions and Intensities in the 2nu4/nu1/nu3 Vibrational System of 14NH3 Near 3 µm.

Line positions and line intensities of the nu1, nu3, and 2nu4 bands of 14NH3 were analyzed using line positions from 0.0054 cm-1 apodized resolution FT spectra recorded at Orsay and using line intensities from 0.011 cm-1 unapodized resolution FT spectra recorded at Kitt Peak National Observatory. About 2110 lines with J' </= 10 were assigned from which 1832 line positions were fitted using an effective rotation-inversion Hamiltonian to achieve an rms of 0.085 cm-1. Nearly 1000 line intensities were measured with an accuracy of 6% or better and modeled to 11 terms of dipole moment expansion to +/-9.4%. The bandstrengths of the nu1, nu3, and 2nu4 bands (determined for the first time in the case of the 2nu4 band) are, respectively, 23.6(2), 11.8(1), and 2.82(4) cm-2/atm at 296 K. A prediction of the line positions and intensities was generated for some approximately 2700 lines with intensities calculated greater than 1 x 10(-4) cm-2 atm-1 at 296 K, suitable for planetological purposes. Tentative assignments involving 22 upper state levels of 4nus2 were identified, but these were not included in the modeling at the present stage. The theoretical model and the set of programs developed for treating the infrared system nu1/nu3/2nu4 of ammonia are briefly discussed. Copyright 1999 Academic Press.