The heat of formation of NaO+(X 3Σ−) and NaO(X 2Π)

High-level ab initio molecular orbital calculations are used to derive ΔHf298[NaO+(X 3Σ−)], with the highest level of theory being RCCSD(T)/aug-cc-pV5Z//UCCSD(T)/aug-cc-pVQZ. Three routes are used to derive this quantity, yielding a final value of ΔHf298[NaO+(X 3Σ−)]=196.5±1.5 kcal mol−1. This value is used in conjunction with the previously derived adiabatic ionization energy of NaO(X 2Π) to yield ΔHf298[NaO(X 2Π)]=22±2 kcal mol−1. These values allow accurate enthalpy changes to be derived for important atmospheric reactions, such as those proposed to account for the formation of sporadic sodium layers, and the Chapman mechanism for the formation of the sodium nightglow.