Fourier-transform microwave spectroscopy of the ClSS radical

The ClSS radical is one of the members of the XSS, XSO and XOO (X = H, F, Cl) radicals. It was studied by Fujitake et al. using millimeter- and sub-millimeter wave spectroscopy, where no hyperfine structure was resolved. As the last piece of this series of radicals, it is important to determine the fine and hyperfine constants of the ClSS radical precisely using FTMW spectroscopy. Different from the case of the ClSO radical with the unpaired electron mainly occupying the S atom at the center, the unpaired electron of the ClSS radical mainly occupies the pc orbital of the terminal S atom. Despite this difference, the investigation of the fine and hyperfine structures of the ClSS radical made us confirm that the XSS and XSO radicals share characteristics in common, but they are quite different from the XOO radicals. The observed spectrum of ClSS showing the fine and hyperfine splittings. Each line splits into two due to the Doppler doubling. ClSS is a member of a series of radicals ClOO, ClSO, and ClSS with the 2A '' ground electronic state.