Accurate variational calculations for line lists to model the vibration-rotation spectra of hot astrophysical atmospheres

The first principles calculation of the spectra of small molecules is making a significant impact on high-resolution spectroscopy as well as astrophysics and atmospheric physics. Variational nuclear motion calculations, combined with high-accuracy ab initio electronic structure computations, are being used to make spectral predictions of increasing accuracy with very few a priori assumptions. This work is important for spectral analysis and particularly for dipole transition intensities, which are often very difficult to measure reliably but are essential inputs for many applications such as modeling of radiative transport and remote sensing. Demands for very extended line lists covering many, many millions of transitions which are required to simulate spectra of hot sources are best met using high-quality theoretical models. This aspect of the use of variational nuclear motion calculations is discussed with reference to both the benchmark water molecule and future data needs, in particular, for models of the atmospheres of extrasolar planets. (C) 2011 John Wiley & Sons, Ltd.