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After x-irradiation of nonstoichiometric BaF 1.1 Br 0.9 , besides the F(Br − ) centre a new intrinsic hole centre was found by electron paramagnetic resonance (EPR). The powder EPR line of this new centre can be simulated assuming an F − 2 molecule on a fluoride site. The new hole centre is stable at room temperature and is the anti-centre of the F(Br − ) centre in the F centre generation process. Magic angle spinning nuclear magnetic resonance (MAS-NMR) experiments on nonstoichiometric BaF 1.1 Br 0.9 show not only resonances of 19 F on regular lattice sites, but also resonances which are due to 19 F on bromine sites ('fluorine antisites'). There are about 10% fluorine antisites in the nonstoichiometric powder which corresponds to the excess fluorine determined by chemical analysis. The generation of F(Br − ) electron trap-hole trap pairs upon x-irradiation originates at the fluorine antisites.