Radiative recombination from states located in the band gap of single‐crystal &agr;‐alumina has been observed by electron‐induced x‐ray emission spectrometry. The variation of intensity as a function of the incident electron beam current has been determined. From this variation, we show that trapping of thermalized incident electrons takes place in the defect sites associated with the observed states. From the binding energies of the states, the sites have been identified as oxygen vacancies. ©1996 American Institute of Physics.