A complete active space self-consistent field multireference configuration interaction study of the low-lying excited states of BrO

A theoretical study of the excited states of the BrO radical has been carried out for the first time using high level ab initio molecular orbital methods. The vertical excitation energies for the low-lying excited states (2 2Π, 1 2Σ+, 1 2Σ− and 1 2Δ) are calculated using the internally contracted multireference configuration interaction (MRCI) method. Based on vertical excitation energies, the ordering of the first few excited states are determined to be 2 2Π, 1 2Δ, 1 2Σ−, and 1 2Σ+. The potential energy curves for the ground state (X 2Π) and several low-lying excited states are examined at the MRCI+Q/aug-cc-pVQZ level of theory. Several excited states are calculated to intersect the 2 2Π state, resulting in predissociation into Br(2P)+O(3P). Results for the quartet states of BrO are also included, as well as calculations of the effects of spin–orbit coupling on the electronic states of BrO. © 2000 American Institute of Physics.