Knowledge Bank

The $O2+$ $b4\sum g$- - $a4\Pi u$ First Negative system has been extended to a new level of the upper state with the measurement of the (3,1) band. This new band and the previously measured bands of this system have been reduced to molecular constants by fitting each band separately and these results have been combined to yield a minimum-variance set of molecular constants for $v\prime \le 3$ and $v\prime \prime \le 6$. It was found that the ``anomalies” in the fine-structure splittings of the $\mathrm{<mrow\; data-mjx-texclass="ORD">4</mrow>}\Pi u$ state can be accounted for fully by the diagonal and off-diagonal elements of the phenomenological spin-spin Hamiltonian, rather than perturbations caused by two $\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}\Pi$ states, as was previously thought. Particular attention has been paid to the correlation between the centrifugal distortion spin-orbit constant $AD\pi$ and the spin-rotation constant $\gamma \pi$. A previously unnoticed possible perturbation in the $\mathrm{<mrow\; data-mjx-texclass="ORD">4</mrow>}\Pi u$ state also has been examined.