Electron paramagnetic resonance and photo-electron paramagnetic resonance investigations were made of the AB3 and AB4 centers found in synthetic diamond crystals. A marked increase in the AB4 electron paramagnetic resonance signal intensity was observed when samples were illuminated with monochromatic light at photon energies greater than 2.06eV. In addition, quenching of the AB3 signal intensity was observed for photo-excitation at photon energies greater than 2.26eV.

Photo-EPR Studies on the AB3 and AB4 Nickel-Related Defects in Diamond. R.N.Pereira, W.Gehlhoff, N.A.Sobolev, A.J.Neves, D.Bimberg: Physica B, 2001, 308-310, 589-92