Knowledge Bank

Over 140 very weak pure rotational distortion moment microwave transitions have been measured for the symmetric top phosphoryl fluoride, $OPF3$ This is the first such spectrum observed in a molecule containing entirely heavy atoms. The observed transitions arose from a small component of the dipole moment induced perpendicular to the symmetry axis by centrifugal distortion, and had the selection rules $\Delta J=0,\Delta K=\pm 3$. Values of K for the transitions were $K=\pm 6\to \pm 9,\pm 7\to 10,\pm 8\to \pm 11,\pm 9\to \pm 12,\pm 11\to \pm 14$, and $\pm 12\to \pm 15$, with values of J ranging from 40 to 80. The Lines were observed between 9 and 18 GHz using our sensitive Stark modulated $spectrometer,1$ and had typical full widths at half maximum of $\sim$1 MHz. The spectrum has yielded on analysis values for $(Ao-Bo)$, two quartic centrifugal distortion constants ($DK$ and $DJK$) and three sextic distortion constants, ($HK,HKJ$, and $HJK$). The value of $(Ao-Bo)$ has been combined with the literature $value2$ for $B0$ to give an improved molecular structure.