Analysis of high temperature ammonia spectra from 780 to 2100 cm-1

A recently-recorded set [Hargreaves et al., Astrophys. J., in press] of Fourier transform emission spectra of hot ammonia is analyzed using a variational line list. Approximately 3350 lines are newly assigned to mainly hot bands from vibrational states as high as nu(2) = 2. 431 new energy levels of these states are experimentally determined, considerably extending the range of known rotationally-excited states. Comparisons with a recent study of high J levels in the ground and first vibrational states [Yu et al., J. Chem. Phys., 133 (2010) 1743171 suggests that while the line assignments presented in that work are correct, their energy level predictions suffer from problems associated with the use of very high-order perturbation series in the effective Hamiltonian. It is suggested that variational calculations provide a more stable method for analyzing spectra involving highly-excited states of ammonia. (C) 2011 Elsevier Inc. All rights reserved.