Nuclear spin–rotation interaction in CF2 (X̃ 1A1) observed by Fourier transform microwave spectroscopy

The rotational spectrum of difluoromethylene (CF2) in its X̃ 1A1 ground electronic state has been observed using molecular beam–Fourier transform microwave spectroscopy. CF2 was produced in a free jet expansion in Ar as inert carrier gas by ArF excimer laser photolysis of CF2Cl2, CF2CHCl, or CF2CHBr or by flash pyrolysis of CF2Br2 in the high-pressure region directly behind a pulsed molecular beam valve. Rotational transitions were observed in the frequency range from 8 to 40 GHz in the CF2 (000) ground vibrational state and in the (100), (010), and (001) excited vibrational states. Several observed lines were split due to the hyperfine interaction between the 19F nuclear spin and the overall rotation of the molecule. The results were used to determine the nuclear spin–rotation interaction parameters for CF2.