Boron-doped diamond layers have been generated in insulating (type IIa) diamonds by means of ion implantation. Cathodoluminescence measurements were used to monitor the layers during this process. It was found that the activation of the boron acceptors, followed by suitable annealing, gave rise to the appearance of two ultraviolet luminescence bands around 3.5 and 4.6 eV. These same bands had been observed previously in natural, as well as synthetically grown, boron-doped, type IIb diamonds. The results reported in this study, support the conclusion that these bands are related to the presence of boron acceptors and show, in addition, that the acceptor density NA need not be more than the density of the compensating donors ND, as had been postulated. © 1998 American Institute of Physics.