Microwave spectrum and quadrupole coupling constant tensor of gauche-isobutyl bromide

Abstract

Microwave spectra of isobutyl bromide have been measured in the frequency region 10–38 GHz. Only a-type R-branch transitions of one conformer, gauche, were assigned. Two hundred and twelve quadrupole hyperfine component spectra were measured for the 53 transitions of the 79Br species and 209 quadrupole hyperfine component spectra for the 54 transitions of the 81Br species. The rotational constants of the ground vibrational state were determined to be A = 7483.20 ± 0.28, B = 1411.1193 ± 0.0057, and C = 1250.5110 ± 0.0056 MHz for the 79Br species, and A = 7481.46 ± 0.51, B = 1398.8805 ± 0.0043, and C = 1240.8924 ± 0.0053 MHz for the 81Br species. From the quadrupole hyperfine splittings of the bromine nucleus, the nuclear quadrupole coupling constants in the principal axes system were determined to be χ aa = 380.0 ± 2.2, χ bb = −144.8 ± 4.1, χ cc = −235.2 ± 4.6, and | χ ab | = 282.5 ± 1.7 MHz for the 79Br species, and χ aa = 302.5 ± 2.0, χ bb = −110.4 ± 3.3, χ cc = −192.1 ± 3.8, and | χ ab | = 236.4 ± 2.0 MHz for the 81Br species.