Accurate energetics for the unimolecular decomposition of HN2

We report internally contracted configuration interaction calculations of the barrier to unimolecular decay of HN2 with cc-pVDZ, cc-pVTZ, cc-pVQZ, and cc-pV5Z basis sets. Extrapolation to the basis set limit gives a barrier height within 0.1 kcal/mol of that used to calibrate the HN2 potential energy surface used by Koizumi, Schatz, and Walch in coupled channel calculations to determine the lifetimes of the lowest vibrational levels of HN2.