Knowledge Bank

A single cavity molecular beam maser spectrometer was used to measure the hyperfine structure of the J $=0\to 1$ rotational transition of $CF3D$ and $CF3H$. The resonance linewidth (F.W.H.M.) was approximately 6 kHz. Using (direct) spin-spin interactions calculated from the molecular structure, the hyperfine spectra were least squares fitted with a theoretical energy expression containing the deuteron quadrupole coupling constant, the fluorine spin-rotation interaction constant, and the hydrogen spin-rotation interaction constant. The resultant values are, for $CF3D$:eqQ = 171.1 $\pm$ 2.0 kHz; deuteron spin-rotation = 3.3 $\pm$ 1.0 kHz; fluorine spin-rotation = 4.7 $\pm$ 1.0kHz. For $CF3H$, the hydrogen spin-rotation constant is 24.5 $\pm$ 3.0 kHz; the fluorine spin-rotation coupling constant is 5.4 $\pm$ 1.5 kHz. The calculated center frequencies for the rotational transition (no hyperfine splittings) are: $CF3D$ = 19 842 217.8 kHz; $CF3H$ = 20 697 690.2 kHz.