RENNER-TELLER EFFECTS IN THE $^{2}\Pi_{i}$ GROUND STATES OF THE SiCH/SiCD and GeCH/GeCD RADICALS

Author Institution: Department of Chemistry, University of Kentucky; Chemistry Department, University of British ColumbiaExtensive emission spectra have been obtained by laser excitation of selected bands of the $\tilde{A}^{2}\Sigma^{+} - \tilde{X}^{2}\Pi_{i}$ systems of jet-cooled SiCH, SiCD, GeCh and GeCD. Up to four quanta of the Si-C or Ge-C stretching mode and even quanta of the bending mode have been observed by pumping upper state $\Sigma$ vibronic levels. Pumping vibronically induced transitions to upper state $\Pi$ vibronic levels has given further information about odd quanta of the bending mode. The assignments have been fitted using a vibronic coupling matrix that includes spin-orbit coupling. Renner-Teller effects. Fermi resonances, and the interaction between nearly degenerate bending levels of different $\nu_{2}$ and K. The emission spectra of SiCH and SiCD, with $A \approx \epsilon\omega$, are easily assigned and the Fermi resonance interaction between $2\nu_{2}$ and $\nu_{3}$ is found to be small. In the germanium species, the spin-orbit coupling is much larger than $\epsilon\omega$ and the spectra are more complicated. Levels of different $\nu_{2}$ with $\Delta\nu_{2} = \pm 1$ are mixed by a $\Delta P = 0, H_{RT} \times H_{SO}$ cross-term of substantial magnitude, disrupting the energy level pattern. Results from the vibronic analyses of all four species will be presented