Collision-induced b(1)Sigma(+)(g)-a(1)Delta(g), b(1)Sigma(+)(g)-X-3 Sigma(-)(g) and a (1)Delta(g)-X-3 Sigma(-)(g) transition probabilities in molecular oxygen

Multireference configuration interaction (MRCI) calculations have been performed for the dipole transition moments of the Noxon band, b(1) Sigma(g)(+)-a(1) Delta(g), and for the red and IR atmospheric emission bands, b(1) Sigma(g)(+)-X-3 Sigma(g)(-) and a (1) Delta(g)-X-3 Sigma(g)(-), in O-2 in collision complexes with different solvent molecules. The spin-orbit coupling between the b(1) Sigma(g)(+) and X-3 Sigma(g)(-)(M-S=0) states does not change after collision so the a-X transition borrows intensity from the collision-induced Noxon band b-a, and the b-X band borrows electric dipole transition probability from the collision-induced difference dipole moments of the b and X states. The calculations show that the b-a, a-X and b-X transition probabilities are enhanced by ca. 10(5), 10(3) and 1.2 times by O-2 + H-2 collisions. An additional order of magnitude enhancement for all three transitions is possible for solvent molecules with larger polarizability than that of molecular hydrogen. The collision-induced b-a transition dipole moment depends not only on the intermolecular distance, but also on the internuclear O-O distance. Since a-X and b-a transition moments are directly connected (D-a,D-X=0.013iD(b,a)), the strong dependence on the O-2 bond length leads to an additional enhancement of the (0,1) vibronic band intensity of the a (1) Delta(g)-X-3 Sigma(g)(-) transition. The dipole moments of the b and X states are also shown to depend on the 0, bond length in the collision complex, which leads to additional collision-induced enhancement of the (0,1) band of the b-X system.