Knowledge Bank

The previously obtained $B~2$A$\prime -X~2$A$″$ and $B~2$A$\prime -A~2$A$\prime$ laser-induced fluorescence (LIF) spectra of jet-cooled cyclohexoxy radical ($c$-C$6$H$\mathrm{<mrow\; data-mjx-texclass="ORD">11</mrow>}$O)\footnote{"Jet-cooled laser spectroscopy of the cyclohexoxy radical'', L. Zu, J. Liu, G. Tarczay, P. Dupr'e, and T. A. Miller, \emph{J. Chem. Phys.} \textbf{120}, 10579 (2004).} have been analyzed and simulated using the coupled-two-state model presented in the preceding talk. The rotational and fine structure of the nearly degenerate $X~2$A$″$ and $A~2$A$\prime$ states is reproduced using one set of molecular constants including rotational constants, spin-rotation constants, effective spin-orbit constants ($a\zeta ed$) and the vibronic energy separation between the two states ($\Delta E$). While the energy level structure could be reproduced by only \emph{effective} spin-rotation constants (without the spin-orbit constant), the spin-orbit interaction introduces transitions that have no intensity using the separate-states asymmetric rotor model. Rotational and fine-structure analysis using the two-state model has proven to be an effective method to separate the first order electron-spin-molecular-rotation constants from the effective spin-rotation constants, and to decouple the spin-orbit splitting ($a\zeta ed$) and the vibronic energy separation ($\Delta E$), both of which contribute to the experimentally observed energy separation between the two coupled states ($\Delta EA~-X~$). Isopropoxy (discussed in the preceding talk), cyclohexoxy, and other molecules in nearly degenerate electronic states provide unique cases bridging the gap from symmetrically degenerate states, e.g., ground $X~2$E state of methoxy, and the Born-Oppenheimer limit of unperturbed electronic states.