DYE LASER EXCITATION STUDIES OF THE $\tilde{A}^{2}\Pi (100)/(020) - \tilde{X}^{2}\Sigma^{+} (020)/(000)$ BANDS OF CaOD: DEPERTURBATION OF THE $(100) {\sim} (020)$ FERMI RESONANCE,

Abstract

The $\nu_{2} = 2$ bending vibrational levels in the $\tilde{A}^{2}\Pi$ and $\tilde{X}^{2}\Sigma^{+}$ states of the CaOD radical have been rotationally analyzed via dye laser excitation of the $\tilde{A}(100)/(020) - \tilde{X}(020)/(000)$ bands. The near degeneracy between the $\tilde{A}(100)^{2}\Pi_{1/2}$ and $\tilde{A}(020)^{2}\Pi_{3/2}$ vibronic components makes it necessary to study the (100)-(020) Fermi diad simultaneously. A global fit of all the observed bands has been performed, employing an effective Hamiltonian that takes account of Renner-Teller, spin-orbit, Coriolis and Fermi resonance interactions occurring in the six $^{2}\Pi$ vibronic components. The Fermi resonance parameter for the CaOD $^{2}\Pi$ state has been determined as $W_{1} = 5.2293(24) cm^{-1}$. Similar previous work for CaOH by the present authors led to the result $W_{1} = 10.3260(5) cm^{-1}$.