Microwave spectrum, rs structure, dipole moment, and nuclear quadrupole coupling constant tensor of ethyl bromide

Abstract

Microwave spectra of ethyl bromide and its 13 isotopic species have been measured. A least-squares analysis of the observed frequencies gave rotational, quartic centrifugal distortion constants and components of the nuclear quadrupole coupling constant tensor. The rs structure has been well established from the observed moments of inertia. The nuclear quadrupole coupling constant tensor in the inertial principal axes system obtained from the spectra could be transformed into that in its own principal axes system which gave the following conclusion. The tensor is roughly cylindrically symmetric around the z axis which is slightly shifted by 50′ from the CBr internuclear line. From the Stark effect measurements of several low J transitions for the three isotopic species, the dipole moment has been determined. For the normal species, μa = 1.951(16), μb = 0.596(12), and μtotal = 2.040(19)D and the dipole moment makes an angle of 5°22′ with the CBr bond inclining its positive pole toward the methyl group.