Comprehensive quantum chemical analysis with the usage of the second-order perturbation multireference XMCQDPT2 approach was carried out to study the processes in the + H ₂ and + H ₂ O systems. The energetically favorable reaction pathways have been revealed based on the exploration of potential energy surfaces. It has been shown that the reactions + H ₂ and + H ₂ O occur with small activation barriers and, primarily, lead to the formation of N ₂ H + H and N ₂ H + OH products, respectively. Further, the interaction of these species could give rise to the ground state and H ₂ (or H ₂ O) products, however, the estimations, based on RRKM theory and dynamic reaction coordinate calculations, exhibited that the + H ₂ and + H ₂ O reactions lead to the dissociative quenching predominately. Appropriate rate constants for revealed reaction channels have been estimated by using a canonical variational theory and capture approximation. Corresponding three-parameter Arrhenius expressions for the temperature range T = 300 − 3000 K were reported.

Multireference ab initio calculations (by using the extended multiconfiguration quasi-degenerate second-order perturbation theory method XMCQDPT2) have been employed to determine the static polarizabilities for the ground triplet ( X 3 Σ g − ) and two excited singlet ( a ¹ Δ _g and b 1 Σ g + ) electronic states of molecular oxygen. The corrections to polarizabilities for the nuclear zero point motion are also reported. It was revealed that the excitation of an O ₂ molecule into the lowest singlet electronic states leads to a decrease in its polarizability: the polarizabilities of O ₂ ( a ¹ Δ _g ) and O ₂ ( b 1 Σ g + ) are smaller (by factors of 0.967 and 0.962, respectively) than that of O ₂ ( X 3 Σ g − ). The theoretical results for the b 1 Σ g + state were quantitatively confirmed experimentally employing the diffraction at laser-induced gratings.