V centers induced by ionizing irradiation at 80 or 300 K in single-crystal and polycrystalline MgAl2O4 samples have been studied by use of electron paramagnetic resonance and optical absorption. Vt- and Vo2- centers, as a result of hole trapping at tetrahedral and octahedral cation vacancies, respectively, have been found to be responsible for two EPR bands centered at g=2.011 and optical absorption bands involved in the complex absorption spectrum at about 3.4 eV. These centers anneal thermally in a very wide step from 220 to 575 K. © 1991 The American Physical Society

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