Knowledge Bank

Deuterium quadrupole splittings of rotational transitions have been observed for benzene-$d1$. for ortho-, meta-, and para-fluorobenzene-$d1$, and for deuterated isothiocyanic acid (DNCS). A gaseous mixture diluted by argon has been expanded through a pulsed supersonic nozzle into an evacuated high Q Fabry-Perot microwave resonator. Highly resolved rotational spectra have been detected with the pulsed excitation and Fourier transform technique. Due to the extremely small dipole moment of benzene-$d1$ the molecules have been excited with microwave pulses of up to 10 W. Deuterium quadrupole coupling constants of benzene-$d1$ and the three fluorobenzene-$d1$ showed little variation.