MICROWAVE-SPECTRUM OF THE FS2 RADICAL IN THE GROUND ELECTRONIC (X)OVER-TILDE(2)A'' STATE

The FS2 radical has been detected in the glow discharge of the SF6 gas by microwave spectroscopy. Both a-type and b-type rotational transiti ons with the fine and hyperfine structure were observed in the millime ter-wave range of 120-185 GHz. The least-squares analysis for the 440 line frequencies led to the determination of the rotational constants, the centrifugal distortion constants, the spin-rotation interaction c onstants with the centrifugal distortion corrections, and the hyperfin e interaction constants. Especially, the off-diagonal constants (epsil on(ab) + epsilon(ba))/2 and T-ab were determined in good precision bec ause some nearly degenerate energy levels were mixed strongly by the o ff-diagonal spin-rotation interaction, which separated the energy leve ls up to 3 GHz and even induced the forbidden transitions to be observ ed strongly. The spin density on the fluorine atom and the chemical bo nd moments were derived for FS2, and the possible signs of T-ab and (e psilon(ab) + epsilon(ba))/2 were discussed. The behaviors of the FS2 r adical and other related transient species in the SF6-discharge system were compared by using the corresponding rotational transitions obser ved in the microwave spectra. (C) 1996 American Institute of Physics.