Microwave Determination of the Centrifugal Distortion Constants of the Methyl-d3 Halides

Measurements of pure rotational transitions ranging from J = 0 — 1 up to J = 8 — 9 have been carried out for the series of deuterated methyl halides listed below in a frequency range from 12 to 152 GHz. Resulting values of the rotational and centrifugal distortion constants B0, DJJ, and DJK, respectively, are: for CD335Cl, 10 841.91 MHz, 10.84 kHz, and 102.7 kHz; for CD337Cl, 10 658.47 MHz, 10.56 kHz, and 99.46 kHz; for CD379Br, 7714.63 MHz, 5.83 kHz, and 63.56 kHz; for CD381Br, 7681.23 MHz, 5.86 kHz, and 63.27 kHz; for CD3127I, 6040.31 MHz, 3.59 kHz, and 48.32 kHz. The quadrupole coupling constant eqQ for the halide nucleus in each of these molecules is, respectively: −74.6, −58.8, 575.7, 480.9, and −1929 MHz. Comparison of the above centrifugal distortion constants with those calculated from known force constants is made.