Adiabatic electron affinity and ionization potential for BrO radical

The adiabatic electron affinity (EA) and ionization potential (IP) for the BrO radical have been computed at high levels of theory. Specifically, the singles and doubles coupled-cluster method that includes a perturbational correction for connected triple excitations, denoted CCSD(T), has been used in conjunction with several one-particle basis sets. The largest basis sets are of the atomic natural orbital (ANO) type and include up through g functions. Our best IP and EA values, 241.1±0.8 and 55.6±1.8 kcal mol⁻¹, respectively, have been obtained by extrapolating the CCSD(T)/ANO results to the one-particle basis-set limit, and are in excellent agreement with the latest experimental values. Our best computed IP shows, definitively, that the experimental result due to Monks et al. is more reliable than the value given by Lias et al. The reliability of our CCSD(T)/ANO calculations is also demonstrated by the excellent agreement between experiment and our best calculations for the BrO and $BrO−$ equilibrium bond distances and vibrational frequencies. Our calculations provide the most reliable equilibrium bond distance, 1.640 Å, and vibrational frequency, 854 cm⁻¹, for $BrO+$ to date, since experimental data are unavailable. Based on the agreement found for BrO and $BrO−,$ we expect the $BrO+$ bond distance and vibrational frequency to be accurate to within ±0.005 Å and ±20 cm⁻¹, respectively.