Identification of the Jahn–Teller active trichlorosiloxy (SiCl3O) free radical in the gas phase.

The à 2A1– X ̃ 2E electronic transition of the jet-cooled trichlorosiloxy (SiCl3O) free radical has been observed for the first time in the 650–590 nm region by laser induced fluorescence (LIF) detection. The radical was produced by a pulsed electric discharge through a mixture of silicon tetrachloride and oxygen in high pressure argon at the exit of a pulsed molecular beam valve. The LIF spectrum shows low frequency intervals, which we assign as activity in the normally forbidden degenerate v 5 ′ and v 6 ′ modes, indicative of a significant Jahn–Teller effect in the ground state. Single vibronic level emission spectra show level dependent spin–orbit splittings in the ground state and Jahn–Teller predictable variations depending on which upper state level is pumped. The measured lower state energy levels have been fitted to a Jahn–Teller model that simultaneously includes spin–orbit coupling and linear and quadratic multimode coupling. In SiCl3O, the Jahn–Teller interaction predominates over spin–orbit effects. [ABSTRACT FROM AUTHOR]