Microwave Spectroscopy of BrBO

The microwave spectra of the four isotopomers of the BrBO molecule (79Br10BO, 81Br10BO, 79Br11BO, and 81Br11BO) 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, nu2 (bend) and nu3 (Br-B str.), for all of four isotopomers, and associated 2nu2, nu2 + nu3, and 2nu3 for the 11B species. The l = 0 substate of the 2nu2 state interacts with the nu3 state through the Fermi resonance. The rotational constants determined for the ground states of the four isotopomers yield the substitution structure, rs(Br&sbond;B) = 1.835791(70) Å and rs(B&dbond;O) = 1.20472(25) Å. The pi character and ionic character of the Br-B bond, which are estimated from the bromine quadrupole coupling constant eQq, are discussed through the comparison with those of related molecules such as BrCN and BrBS. Copyright 1998 Academic Press.