Energy transfer between Tl+‐type impurities in NaCl crystals

We have investigated the energy transfer from Tl+ centers to In+ centers at RT in co-doped NaCl:Tl+, In+ crystals by measuring absorption, photo-excitation, luminescence and time-resolved spectra. The A' luminescence band of the In+ centers is observed under excitation at the absorption band of the Tl+ centers. The A' luminescence band of the Tl+ centers measured at a forward configuration exhibits a dent structure at 4.2 eV corresponding to the A absorption band of the In+ centers. The facts indicate the existence of the energy transfer from the Tl+ to In+ centers through the emission-reabsorption mechanism. On the other hand, the A' luminescence of the Tl+ centers shows a non-exponential decay profile. As the concentration of the In+ centers increases, the non-exponential decay profile becomes faster. The resonance energy transfer giving the non-exponential decay profile is discussed on the basis of the dipole-dipole interaction. (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)