The electric dipole and the nuclear quadrupole moment of methyl bromide in the ground vibrational state

Abstract A set of high-resolution Stark measurements at millimeter-wave frequencies is reported for CH 3 79 Br and CH 3 81 Br. These results are analyzed together with previous data available in the literature to find new sets of molecular (rotational, hyperfine, and dipole moments) constants for both isotopic species. A particular improvement is obtained in the evaluation of the dipole moments, whose values are μ(79) = 1.82171 (26) 0, μ(8l) = 1.82185 (26) D, and for the hyperfine-structure parameters, which are estimated by assuming the most recent model for centrifugal distortion (M. R. Aliev and J. T. Hougen, J. Mol. Spectrosc. 106, 110-123 (1984)), obtaining eqQ 79 0 = 577.1088 (57) MHz, χ 79 J = −0.63 (16) kHz, χ 79 K = 12.6 (16) kHz and eqQ 81 0 = 482.1030 (94) MHz, χ 81 J = −0.57 (17) kHz, χ 81 K = 9.3 (22) kHz.