Microwave Spectroscopy of BrBO

The microwave spectra of the four isotopomers of the BrBO molecule (79Br10BO,81Br10BO,79Br11BO, and81Br11BO) were observed in a dc glow discharge plasma of a mixture of boron tribromide vapor and oxygen gas. Rotational transitions of BrBO were measured for the ground state as well as for the vibrationally excited states, ν2(bend) and ν3(Br–B str.), for all of four isotopomers, and associated 2ν2, ν2+ ν3, and 2ν3for the11B species. Thel= 0 substate of the 2ν2state interacts with the ν3state through the Fermi resonance. The rotational constants determined for the ground states of the four isotopomers yield the substitution structure,rs(BrB) = 1.835791(70) Å andrs(BO) = 1.20472(25) Å. The π character and ionic character of the Br–B bond, which are estimated from the bromine quadrupole coupling constanteQq, are discussed through the comparison with those of related molecules such as BrCN and BrBS.