Ab initio characterization of HBrO2 isomers: implications for stratospheric bromine chemistry

Equilibrium geometries, dipole moments, harmonic vibrational frequencies, and IR intensities are determined for the BrOOH, HOBrO, and HBrO2 molecules using the CCSD(T) correlation method in conjunction with a TZ2P one-particle basis set. Accurate heats of formation are evaluated using the CCSD(T) method together with spdfg one-particle basis sets. BrOOH is the lowest energy isomer, although HOBrO is predicted to be less than 5 kcal/mol higher in energy. The torsional barrier for trans-BrOOH is 2.9 kcal/mol (0 K), while for cis-BrOOH it is 5.4 kcal/mol. BrOOH is shown to be stable with respect to thermal dissociation and implications for stratospheric bromine chemistry are discussed.