Rotational spectrum of HCBr produced by 193-nm laser photolysis of bromoform

The pure rotational spectrum of bromomethylene (HCBr) was studied by kinetic microwave spectroscopy between 420 and 472 GHz. The HCBr radical was produced by 193-nm ArF laser photolysis of bromoform (CHBr₃). More than 130 rotational transitions for both and species in the ground vibrational state were measured involving 1?J?33 and 0?K_a?5. The spectra were well described by an S-reduced Watson Hamiltonian in the I^r representation including the nuclear quadrupole and spin-rotation hyperfine terms. Rotational, centrifugal distortion, nuclear quadrupole and spin-rotation coupling constants were derived for both and species in the ground vibrational state.