Experimental configuration, F-F spin-spin coupling, and potential energy surface of difluoromethane-Ar

The rotational spectra of normal and 13C species of difluoromethane-argon have been investigated by molecular beam Fourier transform microwave spectroscopy. The obtained results allowed for the determination of the configuration of the complex, based on experimental data. The tunnelling splitting originated by van der Waals motions has been determined to be 193.740(1) and 162.16(8) MHz for the normal and 13C species, respectively. The two vibrational splittings have been used to evaluate a tunnelling barrier of 94(5) cm−1. The fluorine-fluorine nuclear spin-spin coupling constant has been determined, Daa = 0.19(1) MHz.