Dibromine monoxide, Br2O: The rotational spectrum and molecular properties

The rotational spectra of Br792O, BrO7981Br, and Br812O in their ground vibrational states as well as Bro7981Br in its v2=1 state have been studied in selected regions between 90 and 523 GHz. Transitions involving a large range of quantum numbers, 6⩽J⩽123 and 0⩽Ka⩽12, have been observed permitting precise rotational and a large set of centrifugal distortion constants to be determined. All isotopic species as well as the excited state data were fit simultaneously. Ground-state effective and average structural parameters as well as an estimate of the equilibrium structure have been derived. The quartic distortion constants were used for a calculation of the harmonic force field. The complete quadrupole tensor has been determined. Its diagonalization reveals a largely covalent BrO bond with little π-bonding. The derived properties of Br2O are compared with those of related compounds such as Cl2O, HOBr, and HOCl.