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The reversible photoinitiated isomerization reaction of BrOBr to BrBrO was measured in solid argon matrixes and calculated by multiconfigurational quasidegenerate perturbation theory (MCQDPT). The calculated vertical excitation energies are in good agreement with the experimentally observed excitation wavelengths. While the isomerization from BrOBr to BrBrO appears to be quantitative, some product loss is observed during the back reaction. The calculated excitation energies and oscillator strengths for transitions from the ground to excited states offer a detailed explanation of this behavior.

The FTIR and UV spectra of OBrO have been measured in solid argon matrices at 17 and 4 K. All three fundamentals of OBrO could be observed. The previously unknown frequency of the bending vibration ( ν 2 ) was located at 317.0/316.3 cm −1 for 16 O 79 Br 16 O/ 16 O 81 Br 16 O and at 302.1/301.4 cm −1 for 18 O 79 Br 18 O/ 18 O 81 Br 18 . OBrO was synthesised by photoisomerising BrOO at 275 nm. The BrOO/argon matrix was prepared by adding bromine atoms from a discharge flow system to molecular oxygen on the surface of a growing argon matrix. We show that the photoisomerisation of BrOO to OBrO is reversible. In addition the wavelength dependency of the OBrO and BrOO photochemistry in argon matrices and the isomerisation rate has been determined in the wavelength range from 200 to 600 nm.