The C-Br photo-fragmentation of bromo-3,5-difluorobenzene (Br-3,5-diFBz) has been investigated using ab initio methods. A reaction coordinate combining a carbon-bromine bond stretch and a bromine out-of-plane bending on the S-1 surface has been found with an activation energy of 2.96 kcal/mol, compatible with the observed picosecond time scale. (c) 2007 Elsevier B.V. All rights reserved.