VIBRONIC STRUCTURE OF THE CCS RADICAL IN THE $\tilde{A}^{3}\Pi_{I}$ STATE

Author Institution: Department of pure and Applied Sciences, College of Art and Sciences, The University of TokyoThe CCS radical was generated in a supersonic jet using a pulsed-discharge of a mixture gas: $C_{2}H_{2} 0.35%/CS_{2} 0.35%$ in Ar. Ro-vibronic spectra of the radical were measured with a LIF spectroscopic method in a spectral region from 900 to 600 nm, corresponding to the $\widetilde{A}^{3} \Pi_{i}-\widetilde{X}^{3} \Sigma^{-}$ transition. In the near infrared region where a photomultiplier has no sensitivity, an MODR technique using an FTMW spectrometer wax employed. Some of the observed bands could be assigned to the $\widetilde{A}(\nu_{1} 00) - \widetilde{X}(000)$ and $\widetilde{A}(\nu_{1} 10) - \widetilde{X}(000)$ transitions $(\nu_{1} = 1,2)$. For the $\widetilde{A}(\nu_{1} 00)$ level, rotational constants were determined using a $^{3}\Pi$ Hamiltonian. Although the $\widetilde{A} ^{3}\Pi_{i}(\nu_{1} 10)$ vibronic level splits into seven levels by the Renner-Teller interaction, transitions to only two of the seven levels from the ground state were observed. Using the two transition frequencies of the $\widetilde{A}(\nu_{1} 10)$ level, the spin-orbit constant, and the position of the $\widetilde{A}(\nu_{1} 00)$ level, the Renner parameter $|\epsilon|$ and the harmonic frequency of the bending motion $\omega_{2}$ in the $\widetilde{A}$ state are estimated to be 0.235 and $402.39 cm^{-1}$, respectively