Nuclear transmutation was used to investigate Cu doping. The Cu atoms were introduced at Zn sites after crystal growth. Because the Cu dopants were introduced after growth, far from equilibrium, they were less able to form complexes with other dopants or lattice defects, as they could do when present during crystal growth. It was found that the results were consistent with CuZn being involved in Cu red and Cu green emissions, but not in I1d excitonic emissions.

E.D.Wheeler, J.L.Boone, J.W.Farmer, H.R.Chandrasekhar: Journal of Applied Physics, 1997, 81[1], 524-6