Abstract
AbstractTwo infrared emission regions (with maxima at 0.803 and 0.723 eV) recently observed by Harami et al. in X‐irradiated KI:PbI2 and the emission regions with maxima at 2.01, 1.79, and near 1.2 eV are studied. The observed emission bands are connected with Hz(Pb2+) centres (Pb2+ ions associated to [I2−]ac molecular ions on anionic (a) and cationic (c) sites). The infrared emission bands of these centres are due to processes occuring in the excited state of the [I2−]ac molecular ion perturbed by the Pb2+ ion. The emission bands are connected with electronic transitions from the tetragonal (2.01 and 1.79 eV peaks) and trigonal (region around 1.2 eV) minima of the triplet relaxed excited state of the Pb2+ ions perturbed by the [I2−]ac ion which can occupy two different positions with respect to Pb2+. The emission band with maximum at 2.05 eV and the region near 1.2 eV are associated to similar transitions in the Pb2+ ion perturbed by the [I3−]aca (V2z(Pb2+) centres) molecular ion. On the basis of these results the optical properties of VL centres (at 0.805 and 0.734 eV), previously observed by Harami et al. in halogen‐excess KI crystals, and assumed here to be the [I2−]ac molecular ions, are also discussed.
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