Beam maser measurements of HDO hyperfine structure

The 431←432, 532←533, and 321←414 transition in HDO were measured in a beam maser spectrometer. Accurate values for rotational transiton frequencies, the deuterium quadrupole coupling tensor, and hydrogen spin-rotation tensor were obtained from the present data combined with previous results on other transitions. Resonance line widths of 2 kHz were obtained for most of the data. Measured quadrupole coupling tensor elements eqQ(D)gg and spin-rotation tensor elements C(X)gg in kHz are as follows: eqQ(D)aa = 276.45±0.88, eqQ(D)bb = −110.97±1.46, eqQ(D)cc = −165.77±1.10, C(D)aa = −1.33±0.20, C(D)bb = −4.38±0.36, C(D)cc = −2.99±0.24, C(H)aa = −58.42±0.47, C(H)bb = −5.46±0.83, C(H)cc = −24.11±0.55.