Rotational analysis of the A2Π u- X2Π g Second Negative band system of O 2+

Abstract

Existing high-resolution data for the O 2 +A 2 Π u - X 2 Π g Second Negative band system have been analyzed using a nonlinear least-squares fit that employs numerically diagonalized Hamiltonians. Values for the full set of molecular constants of the A 2Π u and X 2Π g states are obtained for the first time. In addition to values for ν 0( v′, v″), B v , and D v , the values for the spin-orbit coupling constants A v are determined for both states. For the X 2Π g state, which is near Hund's case (a), the agreement between these A v″ values and those predicted by theory is good. However, for the A 2Π u state, which is much nearer to case (b), these A v′ values and theory disagree both in magnitude and in variation with vibrational level. The A 2Π u state is an inverted state for vibrational levels v′ ≤ 5 and is a regular state for levels v′ = 6–8 (the upper limit of present high-resolution data). Λ-doubling parameters are determined for the X 2Π g state, the only state where Λ-doubling is statistically significant. Spin-rotation interaction is not statistically significant for either state. Dunham Y i0 and Y i1 expansion coefficients are determined for each state. Theoretical D v values calculated from RKR potentials are used to improve the B v values in the reduction of the data.