Knowledge Bank

The rotational spectrum of tricarbon oxide sulphide $C3OS$ has been recorded in the 2 mm region between 118 GHz and 179 Ghz with a new BWO-based millimeter wave synthesizer. Around 12000 rotational transitions could be observed, including transitions of the isotopomers $OCCC33S,OCCC34S,OCC13CS,OC13CCS$ and $O13CCCS$ in natural abundance. The data was analyzed together with hitherto unassigned rotational transitions from previous measurements between 78 GHz and 118 $GHzh$. Our analysis led to the characterisation of various new vibrational sates, especially higher excited states of the lowest-lying bending mode $\nu 7$ in the main isotopomer; So far, highly excited bending states had been known up to $\nu 7=7$ from microwave measurements below 40 GHz. Lately, rotation vibrational TuFIR measurements near 2.4 THz had provided precise term values for the first to the fourth excited state of the bending mode $\nu 7a$. Our new rotational data now allowed us to characterize bending states up to $\nu 7=10$ and higher. Besides the determination of spectroscopic constants for new states, our data also enabled us to improve spectroscopic constants that had been determined from older measurements. Both together extended our knowledge of the structure and the internal dynamics of the linear heterocumulene $C3OS$.