For this purpose, higher level electronic structure calculations are now welcome, both for energies and for spectra. The latter may profit from inclusion of anharmonicity in reduced dimensionality. For the HAT process, semiclassical and quantum dynamics calculations would be particularly helpful to see whether the experimental constraint derived from the spectra is a tight or a loose one. This involves predictions for tunneling in vibrationally excited states of radical complexes which are qualitatively expected to promote the process, but certainly challenging.