Vacuum ultraviolet (VUV) light photolysis of an HBr/O-2 mixture in a Ne matrix has produced HO2Br isomers (HOOBr and HOBrO), which are important reaction intermediates in atmospheric chemistry. The observed bands have been assigned with an aid of a quantum chemical calculation at CCSD/aug-cc-pVDZ. These assignments have been confirmed by the experimental results using isotopic species of O-18(2) or DBr. Their characteristic bands are discussed in comparison with those of HOOCl and HOClO from an HCl/O-2 mixture [7]. Both HOOBr and HOBrO are found to be photolyzed with the UV light below 385 nm. (c) 2010 Elsevier B. V. All rights reserved.