Beam maser spectroscopy on CH3CCD and CD3CCH

Abstract
The J = 1→0 transition frequencies in CH3CCD and CD3CCH were measured using a beam maser spectrometer. Hyperfine structure from deuterium quadrupole coupling was well resolved. The measured deuterium quadrupole coupling tensor components along the symmetry axis are eQqaa = 228±2 kHz for CH3CCD and eQqaa = −55.0±0.5 kHz for CD3CCH. The coupling strength along the bond direction for CD3CCH is eQqzz = 174±6 kHz. These results are compared with the other deuterium quadrupole coupling values. Measured rotational constants are B = 7 778 170±1 kHz for CH3CCD and B = 7 355 767±1 kHz for CD3CCH.