Beam maser measurement of deuterium quadrupole coupling in CD2F2

Hyperfine structure on the 2₂₀ → 3₁₃ rotational transition of CD₂F₂ was measured using a molecular beam maser spectrometer with 6 kHz linewidth (f.w.h.m.). The measured deuterium quadrupole coupling strength along the CD bond direction is eq_zzQ = 186 ± 10 kHz. The best fit asymmetry parameter is η = ?0.15 ± 0.05. Spin-rotation interaction strengths obtained from the spectrum are related to similar terms for CH₂F₂. The center frequency for the observed transition is 22 727 863 ± 2 kHz.